In the Context of Research Using Human Subjects, the Element

In the context of research using human subjects, the element of competence refers to which of the following?

A) The opportunity the patient has to decide whether they will participate in the study on the basis of their own beliefs and feelings
B) The patient's understanding of the legal and ethical aspects of the study.
C) The patient's knowledge that they are participating in a study and informed consent for that participation.
D) The patient's understanding of the treatment, its potential side effects, and their probability of receiving possible outcomes