if当“是否”讲时,引导宾语从句,跟主句时态一致。
例
Ask if he plans to come to the meeting.
问他是否计划来参加会议。
I wonder if you can help me.
不知您是否能帮我的忙？
She asked if I would help.
她问我是否会帮忙。
What if the train is late?
火车要是晚点会怎么样呢？
You may come if you wish.
如果你愿意可以来。
