试题题干
Using whatever cohesive device is appropriate:
We are told that he will come tonight, and if he comes tonight, our meeting will be held tomorrow. If he doesn't come tonight, there won't be any meeting tomorrow.
参考答案
试题解析
if so用来代替前句所说的条件，这样句子会比较简洁。if so是省略了主谓的if状语从句，完整的句子应该是：if that's so或者if it's so