Millie Is Using a Behavior Checklist Strategy as Well as a Prompted

Multiple Choice

Millie is using a behavior checklist strategy as well as a prompted praise strategy when working with her second grade behavior disordered student, Kent. She uses both strategies within the same day going back and forth randomly between the two approaches, while recording his on task behavior.
-In this study, which of the following validity threats does Millie control?

A) Order effects.
B) Selection effects.
C) Treatment effects.
D) History effects.