Children often become surrogate mothers to abandoned animals.
A.substitute
B.temporal
C.affectionate
D.step-
A.substitute
B.temporal
C.affectionate
D.step-
自20世纪90年代初以来,我们用人工授精(artificial insemination)的方法增加大熊猫数量。但是就整个大熊猫家族的命运来说,人工授精的方法远未令人满意。此外,通常大熊猫产生的卵子和精子数量很少,所以当雌性大熊猫无法交配时,这种方法也就起不了作用。1997年,开始实施一个更为雄心勃勃的计划——克隆大熊猫。1998年中国科学院在这个项目上投入了专款,并在1999年得到了科学技术部的资助。这项实验旨在将大熊猫体细胞的细胞核植入去核卵子以造就一个全新的生命。
我们注意到,真正的问题是克隆大熊猫的第二步,即在另一种动物的子宫里(denucleated ovum)培育新的大熊猫。目前我们还无法肯定哪一种动物是理想的“代母体(surrogate mother)”。另一个问题是,即使大熊猫克隆出来,它只有亲本的DNA。因此,在某种程度上,克隆方法是无法保护大熊猫的。
A、They are afraid of getting addicted.
B、They may be dissuaded by side effects of medications.
C、They are likely to mislabel pretreatment symptoms as drug-related.
D、All of the above.
Americans with small families own a small car or a large one. If both parents are working, they usually have two cars. When the family is large, one of the cars is sold and they will buy a van. A small car can hold four persons and a large car can hold six persons but it is very crowded. A van holds seven persons easily, so a family with three children could ask their grandparents to go on a holiday travel. They could all travel together. Mr. Hagen and his wife had a third child last year. This made them sell a second car and buy a van. Their children’s sixth and seventh seats are used to put other things, for a family of five must carry many suitcases when they travel. When they arrive at their grandparents’ home, the suitcases are brought into the two seats which can then carry the grandparents. Americans call van motor homes. A motor home is always used for holidays. When a family is traveling to the mountains or to the seaside, they can live in their motor home for a few days or to the seaside, they can live in their motor home for a few days or weeks. All the members of a big family can enjoy a happier life when they are traveling together. That is why motor homes have become very popular. In America there are many parks for motor homes. After Mr. Hagen and his wife sold their second car, they .
A、sold their old house
B、moved to their grandparents’ house
C、built a new place for a van
D、bought a van
A、pleasant
B、wealthy
C、courageous
D、gaudiness
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