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The human body is incredibly __________. When you donate a pint of blood, you lose about 3.5 trillion red blood cells, but your body quickly replaces them.
A.supple
B.flexible
C.strong
D.resilient
A.supple
B.flexible
C.strong
D.resilient
Why Buy Shade-Grown Coffee?
When people argue about whether coffee is good for health, they&39;re usually thinking of the health of the coffee drinker. Is it good for your heart? Does it increase blood pressure? Does it help you concentrate? However, coffee affects the health of the human population in other ways, too.
Traditionally, coffee bushes were planted under the canopy (树冠) of taller indigenous (土生土长的) trees. However, more and more farmers in Latin America are deforesting the land to grow full-sun coffees. At first, this increases production because more coffee bushes can be planted if there aren&39;t any trees. With increased production come increased profits.
Unfortunately, deforesting for coffee production immediately decreases local wildlife habitat.
Native birds nest and hide from predators (捕食者) in the tall trees and migrating birds rest there.
Furthermore, in the long term, the full-sun method also damages the ecosystem because more chemical fertilizers and pesticides are needed to grow the coffee. The fertilizers and pesticides kill insects that eat coffee plant, but then the birds eat the poisoned insects and also die. The chemicals kill or sicken other animals as well, and can even enter the water that people will eventually drink.
Fortunately, farmers in Central and South America are beginning to grow more coffee bushes in the shade. We can support these farmers by buying coffee with such labels as "shade grown" and "bird friendly". Sure, these varieties might cost a little more. But we&39;re paying for the health of the birds, the land, ourselves, and the planet. I think it&39;s worth it.
What is the main idea of this passage? 查看材料
A.Farmers are changing the way they grow coffee
B.Coffee is becoming more expensive to produce
C.Shade-grow coffee is more expensive than sun-grow coffee
D.People should buy shade-grown coffee
Well, as you are no doubt aware disease-spreading germs or pathogens are everywhere. On a daily basis the human body has to ward off attacks by various harmful bacteria and viruses. A healthy body has a good defence system against many of these germs but the defence only operates well against micro-organisms that it has already encountered, in which case it is said to be immune. There are two ways in which humans acquire natural immunity: actively, when a person has first suffered and then recovered from an illness, and passively, when ready-made protection is transferred into the body, for example, from the maternal blood via the umbilical cord to an unborn child, or through breast milk.
Now, artificially acquired immunity can help the body to fight disease so we can use active immunization as a preventative measure. This is when a person is vaccinated against an illness by injection or oral ingestion of a tiny amount of weakened or inactive germs—not enough to actually cause him or her to contract the illness but sufficient for the body's defence system to recognize and respond to the threat by forming antibodies.
Intervention using passive immunization, on the other hand, is a method of curing an illness after it is too late for prevention. It is less effective than active immunization and takes longer to work. It is used when the body has already been invaded by bacteria and the person is ill. In this case there is no time for the body to make antibodies of its own so proteins—usually taken from the blood of animals—are injected to equip the patient with the essential antibodies to combat the particular illness.
Let's have a quick look at a bit of history: The discovery of vaccination to boost the body's immune system by making it sensitive to particular disease-causing bacteria was made by an eighteenth-century English doctor called Edward Jeanne. He noticed that survivors of smallpox, a common but extremely dangerous disease, never contracted the disease a second time. In other words, they were immune. He studied a similar disease in cows called cowpox and realized that people in contact with the infected cows became ill with symptoms resembling smallpox. However, this disease was quite mild by comparison and those who contracted cowpox were then immune to smallpox. He conducted an experiment by injecting a child with a small amount of pus taken from a cowpox pustule. The child subsequently became ill but soon recovered. Later, he injected the child with pus from a smallpox pustule and the child did not get sick. He had developed immunity to the more dangerous disease. Then antibodies produced to fight the cowpox bacteria had been able to fight off the smallpox bacteria.
What are antibodies? Well, antibodies are made by white blood cells called B-lymphocytes. And this is done in response to the presence of antigens, or other bacterial toxins, which have been released by the micro-organisms (what we commonly refer to as' germs' ) that have invaded the body. These Y-shaped antibodies (or you can think of them as ' antitoxins' ) may stop the toxins or repair the damage they have done by what is known as the antigen-antibody reaction which takes place within the plasma of the blood. A correct antibody (for that disease) clings to a particular antigen in order to render it harmless. Large numbers of these pairs clump together to form. a bigger unit. This is called agglutination and is able to be seen by the naked eye which is very helpful for doctors and other specialists to determine which illnesses a patient is immune to.
Inoculation, or active vaccination, can protect people from serious diseases. The vaccine may make a person feel unwell for a few days when the immune system starts to produce antibodies to match the introduced antigen. This is called a primary reaction. If that particular antigen should ever enter the body again later, a secondary reaction takes place. The body is then able to produce large numbers of corresponding antibodies within a short time so the invading antigens are quickly wiped out without the person suffering any harm from the disease.
Complete the summary below.
Write NO MORE THAN TWO WORDS for each answer.
Every day the human body is fighting off (31) by destructive pathogens. A person in good health has natural protection in the form. of an immune system which works best against familiar microorganisms which may have been encountered during a previous (32) or passed on by the mother before or after birth.
Vaccination is a way to cause (33) immunisation by introducing a small amount of pathogen into the body—just enough for the body's (34) to react by making antibodies. Passive immunization can be used as a way of treating someone who is already sick. Proteins from animal (35) are introduced into the patient to give him the necessary antibodies to fight the disease.
Dr. Edward Jennet observed that people who had suffered and recovered from a serious disease called smallpox did not get it again. He also noted that victims of a milder disease, cowpox, which they caught from (36) , were immune to smallpox. He carried out a successful (37) by deliberately giving a child cowpox in order to make him immune to smallpox.
(31)
A、do
B、doing
C、be done
D、did
A、of
B、with
C、to
D、about
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