1.从属连词：that, whether/if, as if/as though, because,
其中that, whether/if, 在从句中不担任成分，只起到引导从句的功能。that 没有实际意义。if (whether), 意思为 “是否”。
I don’t care about __________ you have money or not.
The problem is __________ Tom is able to arrive on time.
__________ the meeting will be held here is not decided yet.
It looks __________ it is going to rain.
The truth is __________he didn’t come for the concert.
__________ the earth is round is true.
