With a coordinator or subordinator:In time of serious accidents,

With a coordinator or subordinator:
In time of serious accidents, ______we know some basic things about first aid, we can save lives.
【正确答案】：if
【题目解析】：在if引导的条件状语从句中，主句含有情态动词may/might/can/must/should等时，if条件状语从句要用一般现在时。