Which of the Following Statements Regarding Consent Searches Is True

Which of the following statements regarding consent searches is true?

A) The more requests that are made, the more likely it is that there is voluntary consent.
B) An individual who voluntarily turns himself or herself in to the police is less likely to have cooperated with the police.
C) A refusal to sign a form is considered to be controlling instances in which a defendant verbally agrees to a consent search.
D) An individual who receives a warning is less likely to have been coerced into a waiver.