What Is the Purpose of Informed Consent

What is the purpose of informed consent?

A) It means that information a researcher gets from a subject may be used in any way by the researcher, even against the desires, beliefs, or wishes of the research subject.
B) It documents that a researcher has followed the principle of voluntary participation.
C) It gives permission from the government to study certain "taboo" topics.
D) It protects researchers and teachers from outside interference when they debate ideas, investigate issues, or discuss findings.
E) It gives a researcher the right to see government documents.