What Is the Significance of a Contract Being a "Best

What is the significance of a contract being a "best efforts" contract?

A) Such contracts do not meet the consideration requirement, because one party does not have an absolute effort to perform.
B) There is really no significance, because the parties to any contract are obligated to use their best efforts in performing.
C) A promise to use best efforts does meet the consideration requirement, because the duty to use best efforts is a sufficient duty.
D) These are contracts where one party agrees to buy all that the other produces, but they do not meet the consideration requirements because the other party might produce nothing.
E) Such contracts meet the consideration requirement because they are considered implied-in-fact contracts.