题型:问答题 简答题 Jim went swimming with his parents yesterday afternoon. _______. [ ]A. So did Mary B. So Mary doesC. So Mary was D. So Mary did 查看答案
题型:问答题 简答题 如图所示,空气中有一块横截面呈扇形的玻璃砖,玻璃砖的折射率为2.现有一细光束垂直射到AO面上,经玻璃砖反射、折射后经OB面平行返回,∠AOB=135°,则光线在OB面上的入射角应是( )A.15°B.30°C.45°D.60° 查看答案