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 kilometres 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 tune 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.
The word "exemplified" in the passage can be replaced by...................................
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Lời giải:
Báo sai- exemplify /ɪɡˈzemplɪfaɪ/ ~ illustrate /ˈɪləstreɪt/ (v): minh họa
- specify (v): chỉ rõ, ghi rõ
E.g: He said we should meet but didn't specify a time.
- resemble (v): giống với
E.g: You resemble your mother very closely.
- justify (v): biện hộ, bào chữa
“The basic principle of radar is exemplified by what happens when one shouts in a cave.”
(Nguyên tắc cơ bản của hệ thống radar được minh họa bằng những gì xảy ra khi một người hét lên trong một hang động.)
=> Đáp án A