选择：-------It is hot today,-----it?-------Yes,Let us go-----------.
A.is swimming B.is not swimming C.is not swim
是不是选B.为什么要否定的呢?
------It is hot today,-----it?
-----Yes,Let us go-----------.
A.is swimming B.isn't swimming isn't swim
原题是这样的，不知为什么就变成上面那样的了？的确上面的有点乱。