With trees _______ in the storm, I don’t think it is a good idea to step out as our flimsy little car wouldn’t stand much of a chance.

blowing over (a)    is incorrect as “breaking out” is a phrasal verb that indicates “escaping”. (b)   is incorrect as “blowing off” means “to disregard something” or “to forcibly uproot something, especially with an explosive”. (c)    is incorrect as “breaking up” is a phrasal verb that indicates “to end a relationship”. (d)   is incorrect as “blowing out” is a phrasal verb that indicates “to extinguish”, usually a flame. (e)    is correct as “blowing over” means to get knocked down by wind– that fits here grammatically and meaningfully.