問題詳情

Echolocating bats 21 sounds in patterns—characteristic ofeach species—that contain both frequency-modulated (FM) andconstant-frequency (CF) signals. The broadband FM signals andthe narrowband CF signals travel out to a target, reflect from itand return to the hunting bat. In this process of 22 andreflection, the sounds are changed and the changes in the echoesenable the bat to perceive features of the target.The FM signals report information about target characteristicsthat modify the timing and the fine frequency structure, orspectrum, of echoes—for example, the target’s size, shape,texture, surface, structure, and direction in space. Because oftheir narrow bandwidth, CF signals portray only the target’spresence and, 23 some bat species, its motion 24 thebat’s. 25 changes in the CF echo’s frequency, bats of somespecies correct in flight for the direction and velocity of theirmoving prey.
21.
(A) break out
(B) emit
(C) remit
(D) burst into

參考答案

答案：B
難度：非常困難0
統計：A(0),B(0),C(1),D(0),E(0)

內容推薦

內容推薦