1. Kraft Foods is testing a new breakfast cereal which was found to be tastier than the competitor after a three week in home trial. The experimental group was given the new cereal, the control group was given the competitor's cereal. Later it was learned that many people dropped out of the study because they didn't like the new cereal. Which of the following threats to internal validity is most likely:
a. History
b. Maturation
c. Mortality
d. Sampling bias
e. Instrumentation