Juxtaposition is a term for the placement of two things close together for simultaneous examination (and contrasting effect).
Oxymoron relies on the juxtaposition of two words that have conflicting meanings that would normally negate each other Jumbo shrimp was an excellent example of this. A more tongue-in-cheek example is military intelligence.
Paradox is more of a logical device than a literary device in which two or more axiomatically true items are juxtaposed to be in contradiction to one another. Unlike an oxymoron, it does not have to be based solely on the literary meaning of those terms.
There is a classic religious paradox, namely, Can God create a substance so heavy that He Himself could not lift it? The paradox being an omnipotent being can lift anything, because he is omnipotent; he can also create anything because he is omnipotent. So, how can both states be true simultaneously. The answer: they can't. But, which one is untrue? You cannot say, because, both parts are axiomatic and untestable.
Oh, and, do your own homework next time!!!! :-P