The sentence that features a present participial phrase functioning as an adjective is the one that reads as follows: Blushing furiously the newcomer, couldn't believe he'd been so gullible.
Participial phrases add a description to the sentence. In this case, the information added is related to the noun it modifies ("the newcomer"). This can be seen when we ask the following question: Who blushed furiously? The newcomer.
The answer would be A. You would be trying to convince why they should build a skate park. So you would include your reasoning why it would be good for the community.
