When La Greca et al. (1996) studied children over a period of 10 months after they had gone through a severe hurricane, they examined the effect of attrition. They discovered that

a. their results were severely compromised because the most severely affected children dropped out of the study.
b. over half of the children dropped out of the study by the end.
c. although there was about 20 percent attrition, those who dropped out of the study didn't seem to differ from those who remained.
d. they could reduce attrition by waiting until the children stabilized after the hurricane so those who remained didn't drop out of the study.

c