You should read this . Here is just a part of it: There are a number of particles ( up, down, in, out, on, off, away, back ) which should make us very suspicious that we are dealing with a separable phrasal verb, and a number of them ( with, without, by, for, at, across, of, from, to, into ) which almost certainly indicate a prepositional verb. But there are some strange cases!
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