A Collateral Contract Is

A collateral contract is

A) an unenforceable agreement that is related to another written agreement.
B) a separate agreement between the parties included in a written contract.
C) an agreement between parties to a contract that precedes another written agreement.
D) a separate agreement between the parties made at the same time as a main agreement between the parties,but not included in the written document.
E) a void agreement that is related to another written agreement.