光在真空中的传播速度为3×108m/s,为实现我国的探月计划,向月球发射的激光到达月球并返回地面约需2.6s,则地球和月球之间的距离是 m。
3.9×108
— Your watch is so beautiful. It must be expensive.
— Not at all. I only _____ ¥20 on it. [ ]
A. cost
B. spent
C. paid
D. took
新设立中介服务机构的房地产估价机构资质等级应当核定为三级资质,设( )年的暂定期。
A.1 B.2 C.3 D.5