[填空题]Every word has a kind of secret story in it just (76)
as "hello" has. Each word is a puzzle. Some of (77)
the puzzles are easy to solve. A word "breakfast" (78)
for example, it is made up of two smaller words, (79)
break and fast. You know what break means and that for (80)
someone fasts, it means he doesn’t eat. More people (81)
fast from time they go to bed until they get up in (82)
the morning. They broke their fast when they eat (83)
their morning meal—breakfast. And some (84)
word puzzles are a little harder to solve them. (85)

A new kind of radar has been developed for spaceship travelers. A working laboratory model of a new system of radar that makes use of a beam of light is said to be ten thousand times more accurate than the best comparable system of radar that used microwaves.
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 cycle
A. laser-doppler radar is more accurate than microwave radar
B. microwave radar may not ensure absolute precision in measuring varying speeds
C. the light-beam radar can measure only slow speeds with accuracy
D. microwave radar operates at a higher frequency than laser-doppler radar