Why Is the Administration of a Pretest a Cause for Concern

Why is the administration of a pretest a cause for concern in a research study?

A) It is a threat to internal validity, as it may affect the posttest results.
B) It is a threat to external validity, as it may affect the posttest results.
C) It is a form of selection bias that contributes to the problem of maturation.
D) It is a form of maturation that contributes to the problem of selection bias.