To be on the safe side we should fill up the tank now because we run out of gas on the

问题补充：

To be on the safe side, we should fill up the tank now, because we run out of gas on the way.

A. could

B. might

C. would

D. must

答案：

A. could

(答案→)B. might

C. would

D. must

解析： to be on the safe side为慎重起见。might表示可能性推测。