题目内容
（请给出正确答案）
Radar makes the most accurate determination of the ______．
A.direction of a target
B.distance to a target
C.size of a target
D.shape of a target
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更多“Radar makes the most accurate …”相关的问题
Laser-doppler radar makes use of______.
A．light
B．microwaves
C．sound waves
D．both A and B
Laser-doppler radar makes use of______.
A．light
B．microwaves
C．sound waves
D．both A and B
The model has shown that this radar system, known as laser-dopple radar, can measure with absolute precision speeds varying from spaceship orbital injection(进入)velocities(速度)of five miles per second down to virtual stops-speeds of less than one-thousandth of an inch per second. According to the scientists who are developing this system, such fine measures of velocity are of prime importance in space missions. In a rendezvous(对接) between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip open a ship's skin, or a nudge could knock the station out of its orbit.
The light-beam radar, which operates at a frequency of trillions of cycles(百万兆) per second, could easily detect and measure the movement of a vehicle edging up to a satellite space station. A control system using so precise a signal as this would allow a huge vehicle to dock at a space station as lightly as a feather.
Laser-dopple radar ______ .
A．measures the movement of a spaceship by means of light beam
B．makes use of microwaves
C．makes use of sound waves
D．both A and B
A．Commercial airliners are already required by law to be equipped with extremely sophisticated radar systems.
B．Centrally located airports are experiencing overcrowded airspace primarily because of sharp increases in commercial-airline traffic.
C．Many pilots of private planes would rather buy radar equipment than be excluded from centrally located airports.
D．The number of midair collisions that occur near centrally located airports has decreased in recent years.
E．Private planes not equipped with radar systems cause a disproportionately large number of midair collisions around centrally located airports.
The model has shown that this radar system, known as laser-doppler radar, can measure with absolute precision speeds varying from spaceship orbital injection (进入) velocities (速度) of five miles per second down to virtual stops--speeds of less than one ten thousandth of an inch per second. According to the scientists who are developing this system, such fine measures of velocity are of prime importance in space missions. In a rendezvous (对接) between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip open a ship's skin, or a nudge could knock the station out of its orbit.
The light-beam radar, which operates at a frequency of trillions (百万兆) of cycles per second, could easily detect and measure the movement of a vehicle edging up to a satellite space station. A control system using so precise a signal as this would allow a huge vehicle to dock at a space station as lightly as a feather.
Laser-doppler radar ______. ()
A．measures the movements of a spaceship by means of light beam
B．makes use of microwaves
C．makes use of sound waves
D．Both A and B
A.makes use of microwaves
B.measures the movements ofa spaceship by means of light beam
C.makes use of sound waves
D.Both A and B
What is the most important reason that makes people eat？
A．Physical need.
B．Physical desire.
C．Psychological need.
D．Psychological desire.
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