Dr Mokoena Believes That People Who Are Under Stress Will

Multiple Choice

Dr Mokoena believes that people who are under stress will develop more colds than people who are not under stress.When he randomly selects 10 participants and exposes them to high levels of stress, he finds that 9 of the participants develop colds.Based on these results he concludes that stress causes an increase in colds.Dr Mokoena's reasoning may be flawed because in this study

A) there was no dependent variable in his study.
B) there was no control group for comparison.
C) he didn't formulate a hypothesis before he collected his data.
D) he didn't measure the independent variable when the study ended.