Final answer:
Voluntarily giving up a known right is called a C. waiver, which can be related to legal contexts such as expatriation or rights of the accused under the Bill of Rights.
Step-by-step explanation:
Giving up a known right voluntarily is called a waiver. This legal term indicates that a person has intentionally given up a right or privilege, often by a statement or by conduct. An example of this in the context of American law is the act of expatriation, where one may voluntarily give up their citizenship, a right provided since 1868.
In other legal contexts, rights such as the right to remain silent and the right to legal counsel, which are part of the rights of the accused under the Bill of Rights, can also be waived. However, the Bill of Rights does not guarantee the right to an education; thus, such a right cannot be waived under its protections.