QUESTIONS 61 - 64. MARK THE LETTER A, B, C, OR D TO INDICATE THE BEST...

Câu 50: The word “hybrid” in paragraph 4 is closest in meaning to___.A.

combination

B. hazardous C. futuristic D. automatedĐọc kỹ đoạn văn sau và chọn phương án đúng (A hoặc B, C, D) cho mỗi câu từ 51 đến 60:

A pilot cannot fly by sight alone. In many conditions, such as flying at night and landing

in dense fog, a pilot must use radar, an alternative way of navigating. Since human eyes are

not very good at determining speeds of approaching objects, radar can show a pilot how fast

nearby planes are moving. The basic principle of radar is exemplified by what happens

when one shouts in a cave. The echo of the sounds against the walls helps a person

determine the size of the cave. With radar, however, the waves are radio waves instead of

sound waves. Radio waves travel at the speed of light, about 300,000 kilometers in one

second. A radar set sends out a short burst of radio waves. Then it receives the echoes

produced when the waves bounce off objects. By determining the time it takes for the

echoes to return to the radar set, a trained technician can determine the distance between the

radar set and other objects. The word “radar”, in fact, gets its name from the term “radio

detection and ranging”. “Ranging” is the term for detection of the distance between an

object and the radar set. Besides being of critical importance to pilots, radar is essential for

air traffic control, tracking ships at sea, and for tracking weather systems and storms.