Sam’s parents workers in that hotel. [ ]
A. is
B. am
C. are
答案：C
南极洲至今无人定居，主要原因是
A．常年冰雪覆盖
B．沙漠广布
C．和平利用与保护
D．水资源丰富
柴油机润滑间隙过大有何害处？
