THE WORD “HYBRID” IS CLOSEST IN MEANING TOA. COMBINATION B. HAZARDOUS...

Câu 50: The word “hybrid” is closest in meaning toA. combination B. hazardous (mạo hiểm) C. futuristic D. automatedVII. Read the following text then answer the questions that follow by circling its corresponding letter marked A,B, C, or D.A pilot cannot fly by sight alone. In many conditions, such as flying at night and landing in dense fog, a pilotmust use radar, an alternative way of navigating (định vị). Since human eyes are not very good at determining speeds ofapproaching objects, radar can show a pilot how fast nearby planes are moving. The basic principle of radar isexemplified (minh họa) by what happens when one shouts in a cave. The echo of the sounds against the walls helps aperson determine the size of the cave. With radar, however, the waves are radio waves instead of sound waves. Radiowaves travel at the speed of light, about 300,000 kilometers in one second. A radar set sends out a short burst of radiowaves. Then it receives the echoes produced when the waves bounce off objects. By determining the time it takes forthe echoes to return to the radar set, a trained technician can determine the distance between the radar set and otherobjects. The word “radar”, in fact, gets its name from the term “radio detection and ranging”. Ranging” is the term fordetection of the distance between an object and the radar set. Besides being of critical importance to pilots, radar isessential for air traffic control, tracking ships at sea, and for tracking weather systems and storms.