--- I called Nina several times, but she didn't answer.

--- Of course, she ____________ London for a visit. [ ]

A. has been to        

B. has gone to    

C. has been in        

D. had gone to

在1:1000地形图上，若等高距为1m，现要设计一条坡度为4%的等坡度路线，则在地形图上该路线的等高线平距应为______m。