If participants in the experimental group and control group differ significantly, this may directly threaten the ________ validity of the study.

A) construct
B) internal
C) face
D) extraneous

Internal validity refers to the degree to which a study measures what it claims to measure, without interference from extraneous variables. If participants in the experimental group and control group differ significantly, this may suggest the presence of an extraneous variable that is influencing the results, which would undermine the study's internal validity. Construct validity refers to the degree to which a study's measurements, methods, and operational definitions accurately reflect the underlying constructs that they intend to assess. Face validity refers to the degree to which an experiment appears to measure what it is supposed to measure, on the surface. While extraneous variables can certainly threaten the validity of a study, B is the best answer.