Which of the Following Propositions Is TRUE in the Context

Which of the following propositions is TRUE in the context of the doctrine of promissory estoppel?

A) The representee cannot rely on the representor's gratuitous promise if the representor was guilty of inequitable behaviour.
B) Once legal rights are affected by the doctrine of promissory estoppel, they can never be revived.
C) Promissory estoppel can only be based on representations of existing or past facts.
D) The doctrine of promissory estoppel is effective only if the representee relied upon a statement by the representor.
E) Promissory estoppel can be used as a sword but not as a shield.