correct words and sentence

Both sentences have incorrect punctuation. You never put a single comma between a subject and a predicate. The first is worded correctly but needs to have the comma removed.

As for the words in bold type, "aforementioned" means mentioned before this line, but your sentences are after. As for "supplied," it too is wrong, since it's in past tense. How about rewriting that line as, "Which sentence below is better?" (Note, you can't use "best" since you have only two choices. The correct word to use when comparing two items is "better.")

Thanks.

What would be the best choice for the aforementioned sentence I have supplied?

Is the word in bold correct? I think it should be 'provided'.

If you decide to use that sentence, yes, "provided" is a better choice.