单选题 Cosmic rays of various kinds come through the air from outer space, but enormous quantities of radiation from the sun are ______ off.
A. avoided B. excluded C. screened D.separated

【正确答案】 C
【答案解析】screen off隔开。句意：宇宙中的各种光线从外层空间通过大气层传来，但是太阳的大量辐射能被大气层隔开。A. avoid避免；B．exclude排除；D．separate使隔开，其后不跟off。