Which of the Following Is a Doctrine by Which Courts

Multiple Choice

Which of the following is a doctrine by which courts imply,as a matter of law,a promise to pay the reasonable value of goods or services when the party receiving such goods or services has knowingly done so under circumstances that make it unfair to retain them without paying for them?

A) Quasi-contract
B) Freedom of contract
C) Promissory estoppel
D) Implied in law contract