Use of a Pretest as Well as a Posttest, Rather

Multiple Choice

Use of a pretest as well as a posttest, rather than a posttest by itself, is valuable because

A) One can evaluate and statistically adjust for any pretest sensitization effect
B) One can use a directional test to evaluate change, i.e., did patients improve
C) Reduces bias due to multiple statistical tests
D) The error term is reduced in the statistical test and power is increased