It’s always best to have a good subject mix/balance for SAT II’s, and also to contrast your résumé or in-school strengths with strong test scores in other subjects. For example, if you’re great at math, do a bunch of math extracurriculars, and crush math in school, then taking the SAT Literature subject test would be a great contrast.
Based on what you said, I highly suggest you take a Subject Test in the Humanities. US History is a good one if you’re an international student (proves your bonafides); Literature is always good. Taking in a foreign language is generally useless, so don’t bother with that.
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