一束光在空气中经过凸透镜折射后[ ]
A.一定是平行光
B.一定会聚到一点
C.一定是发散光
D.一定比原光束会聚一些
答案:D
People prefer ______ TV or listen to music rather than ______ newspapers to relax themselves. [ ]
A. watching; read
B. watching; to read
C. to watch; read
D. to watch; reading
()表示班轮航线上各港口的平均装卸效率和组织管理水平,决定着航线上船舶的在港时间的班轮航线参数是航线平均装卸总定额。
A.正确
B.错误