One way to test for the validity of research methods is to

A. compare children’s answers to different halves of the same test.
B. test for inter-rater reliability.
C. compare children’s answers on different forms of the same measure.
D. see how effective the measure is in predicting behavior it would reasonably expect 
to predict.

D?

That's one way, yes.

Correct! One way to test the validity of research methods is to see how effective the measure is in predicting behavior it would reasonably expect to predict. This is known as predictive validity.

To determine the predictive validity, researchers would collect data using a particular research method or measure and then compare those results to the behavior or outcome that the method is expected to predict. For example, if a measure claims to accurately predict academic performance, researchers would examine whether the scores obtained from the measure are indeed related to the actual academic performance of the individuals being studied.

This type of testing helps to establish the validity of a research method by assessing whether the measure is capable of accurately predicting the behaviors or outcomes it claims to measure.