Why Is There No Consideration When a Party Does What

Multiple Choice

Why is there no consideration when a party does what it is already legally obligated to do?

A) Because there will not be adequate consideration.
B) Because promising to do something you are obligated to do is an illusory promise.
C) Because of the legal doctrine of promissory estoppel.
D) There is no consideration when a party does what it is legally obligated to do.
E) Because there is no detriment.