Suppose You Have Data on Standardized Test Scores for a Sample

Suppose you have data on standardized test scores for a sample of high school juniors and seniors.You could test for the possibility that senior outperform juniors,holding all other independent variables constant,by

A) directly entering junior and senior into your regression.
B) including a binary dummy variable that is equal to 1 for seniors and 0 for juniors in your regression.
C) including quadratic terms for junior and senior in your regression.
D) estimating separate regressions for juniors and seniors.