Time to bust it for the rest of the year. Later, in your application essays when you write about overcoming a tough spot, you can write about how you struggled in chem when you were a sophomore and how you got additional tutoring, met w/ teacher, studied, etc, etc, and figured out how to beat that class and make an A. This is an opportunity to show you can do hard work, so take advantage of it! Cadets face similar situations daily. Show that you have what it takes.