A Researcher Tests a New Intervention for Nausea Associated with Chemotherapy

A researcher tests a new intervention for nausea associated with chemotherapy, in hospitalized patients. At the same time, a new over-the-counter medication containing natural herbs is marketed aggressively, and some of the hospital patients are given this herbal remedy by their families. This is a threat to which type of validity?

A) Construct validity
B) Internal validity
C) External validity
D) Statistical conclusion validity