Only when     possible to settle the problem.[ ]

A. does the editor come will it be    

B. the editor comes will it be

C. has the editor come it will be    

D. the editor comes it will be

一辆汽车在高速公路上行驶的速度是每小时90千米，是在普通公路上行驶速度的2倍．这辆汽车在普通公路上行驶的速度是每小时多少千米？