Melissa has agreed to participate in a 90-day study of food preferences among adolescents. After participating for two weeks, Melissa wants to withdraw from the study because it is taking too much of her time. According to the APA guidelines

A) Melissa has to give the researchers a two-week notice before she can withdraw.
B) Melissa can withdraw at any time.
C) Melissa cannot withdraw once she has signed an informed consent form.
D) Melissa can withdraw only if she has a valid reason, such as a health issue or family emergency.