IDNLearn.com: Where your questions meet expert advice and community insights. Get thorough and trustworthy answers to your queries from our extensive network of knowledgeable professionals.

Lisa's study assessed the effects of an intervention to facilitate the math skills of low-achieving second grade learners. She administered a treatment to the students in the form of structured computer lesson and found that students' skills increased. With which validity threat should Lisa be most concerned?
A) Instrumentation
B) Statistical regression
C) History
D) Mortality