题目

The train leaves at 6:00 p.m. So I have to be at the station ____5:40p.m.at the latest. A. until               B. after                     C. by                             D. around    答案：C莫霍界面是下列哪一组地理圈层的交界面 A.地壳—地核  B.地壳—地幔  C.地幔—地核  D.岩石圈—水圈