Question

You ______ take out the dog now,and you can'tdo it later. A haven't to B don't have to C have to

D must

Answer 1

C 你现在必须把狗带到外面去，一会就不行了。
根据后面的话显然前面是必须的意思，而且是客观上不得不这样做，所以用have to
不用must

Answer 2

D 你必须现在把狗带出去，并且你不能过一会儿在再出去。
是命令语气。