Mehmet Is Conducting a Study Aimed at Improving the Problem

Multiple Choice

Mehmet is conducting a study aimed at improving the problem solving abilities of older adults.Prior to the intervention,all of the participants are given a series of problems to solve and,in the process of trying to solve them,many of the participants refine their approaches to problem solving.As a result,Mehmet's study has a(n) ____ threat.

A) history
B) maturation
C) instrumentation
D) testing