Witch sentence uses the the dashes correctly a: there will be alot of people at graduation -- and maybe some free food. b: there will be -- alot of people at graduation and maybe some free food. c: there will be alot of people -- at graduation and maybe some free food.

The correct sentence is (A).

In (A), the dash correctly adds in an additional thought: "and maybe some free food".

In (B), the dash in between "be" and "a lot" interrupts the sentence at a strange place that causes the reader to read it like there is a hiccup there.

In (C), again, like (B), the dash is in a strange places that interrupts the sentence.

Thus, the answer is (A).

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c. to depict the cunningness of the federal soldiers