The plane _____ (take) off in an hour.If you ______ (not start) at once, you____ (miss) it.

will take
don't start
will miss

is going to take 或者is to take
（这两个都是表计划要进行的事）

don't start
will miss
（这是主将从现）

will take
don't start
will miss
祝你成功！

will take don't start will miss 希望对你有帮助

will take. 因为有“in an hour”，表明用将来时。
don't start. will miss.“if”引导的宾语从句，句式“主句+if+从句”或
“If+从句 ，主句”。

is taking,
dont start,
'll miss.

我也要这样写作业，呵呵。。。