Which of the Following Is an Example of a Formal

Which of the following is an example of a formal contract?

A) Contracts under seal but not executed contracts or letters of credit.
B) Executed contracts but not contracts under sale or letters of credit.
C) Letters of credit and contracts under seal, but not executed contracts.
D) Contracts under seal letters of credit, but not executory contracts.
E) Contracts under seal, letters of credit, and also executed contracts.