<p>My advice is to just take the environmental science test. I did that this year, with only about 2 days of review out of the barrons book (as well as a 6 page cram sheet), and I’m pretty sure I got a 4 or a 5.<br>
Environmental is an interdisciplinary science that overlaps a ton with geography, biology, and chemistry(and common sense). Having also taken these three exams, there was very little new information I needed to learn to fill the gaps. Since you are already in bio and chem, I would go for environmental science.</p>