Question

It will all evaporate and go back to the moon. Therefore, you must be very quick about it. ( Join using an adverb clause)

Answer 1

A 1 -

Because it will all evaporate and go back to the moon, you must be very quick about it

A 2 -

You must be very quick about it because it will all evaporate and go back to the moon

you could even use as, so