158. Since the start of the space age, more and more littering has occurred in orbits near Earth, often because the intentional discarding of lens caps, packing material, fuel tanks, and payload covers. A. more and more littering has occurred in orbits near Earth, often because B. orbits near Earth have become more and more littered, often from C. orbits near Earth become littered more and more, often resulting from D. there have been more and more littering of orbits near Earth, often because of E. there had been littering more and more of orbits near Earth, often with
A: because 后面不是完整的句子 B: correct C: become要变成have become D: there have been 错 E: 同上
请教:一直记得象become这类趋向性动词一般是不用完成时态的,虽然我也知道since是完成时的标志,不过总还是觉得答案中的表达方式有待商榷,请NN指点,谢谢! |