在高速行驶时，降低空气阻力可显著提高燃油经济性。
参考答案：对
29. A man who witnessed the accident said that the car _____ at nearly 100 kilometers per hour at the time.
A．was going
B．is going
C．had gone
D．has been going
船舶电台NBDP设备电传应答码（）组成
A.选呼码
B.船名缩写（或呼号）
C.字母X
D.都是
