请问下面这些短语怎么造句呀？1)in the case of 2)from time to time 3)on the one hand

1 we shoud bring some medicine for our trip in case of emergency.
2 she takes a trip from time to time.
3 using internet is a good thing,but on the other hand, we may spend too much time on it.

from time to time有时，相当于sometimes
in case of 以防万一