<p>It seems like we are only required to take 2.</p>
<p>depends on the school. For example Georgetown requires 3</p>
<p>Well, most universities like MIT Stanford require you to take 2 subjects test. However, taking 3 exams will increase you odds to get a satisfactory score. For example, you do well in Math, Phy and Chem, if you take two of them, you might get 780 800, but if you still take another, you get a chance to get 780 800 800 or 780 800 790. Then you can simply select two of them to send.</p>