Only A and C . The other two are impossible.
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Anonymous my suggestion on the above - They have decided to ask for the cops help. How is this?That is OK if you add an apostrophe, but it is irrelevant to the question that was asked.
GuyperA. "He's out of town doing some research"B. "He's out of town to do some research"Both of those are possible. A is more likely, I think.