What subject test to take? (international student)

<p>Hey
I am an international student that's gonna take two subjects this fall. I will take SAT math II and World History, but because the world history is in December and that some schools require 3 subject tests, I need to take a third subject.
I'm not good in any of the languages, and the same with literature, that means only science and US history is left. I haven't study any US history and I have only a basic knowledge of bio, chem and physics. So my question is, which of bio, chem, physics and US history is easiest to self-study with only basic knowledge?</p>