---they have found someone in trouble,they decide on suitable ways to help them.
问题描述：
---they have found someone in trouble,they decide on suitable ways to help them.
A If B Once C Because D Since
如何区分A\B两个答案?
答
B吧
A是虚拟,虚拟条件句时态要比结果句时态过去一个等级
如果A后面应该是will decide
而且have found暗示是once