What Was the Main Methodological Flaw in Brady's "Ulcers in Executive

Multiple Choice

What was the main methodological flaw in Brady's "ulcers in executive monkeys" study?

A) because the animals were in restraining chairs for so long, a maturation effect occurred
B) the executive monkeys were more ulcer-prone than the control group monkeys
C) because the study was completed in another historical era, there is no external validity
D) because most of the monkeys died, attrition was a problem