Can I use they instead of he or she in formal writing?

Jenna stood in front of the closed door. she knew she hadevery right to be here. your exam scores are just as high ascora's, she said to herself. there's no reason you shouldhave been left off the math team while cora was namedcaptain. she had never been one to rock the boat, but shecouldn't just let this lie.she pushed the door open and saw ms. jenson, the mathteam advisor, sitting at her desk. "ms. jenson? can i talk toyou for a minute? " her voice wavered, but she tried to lookconfident."sure," said ms. jenson, "but i hope this isn't about namingcora captain of the math team. i'm afraid my decision isfinal."jenna took a deep breath and prepared to plead her case.which statement best describes the external conflict in this passage?