Which of the Following Is Correct with Regard to an Accountant's

Which of the following is correct with regard to an accountant's contractual liability?

A) An accountant is bound to perform all the duties she explicitly agrees to perform.
B) An accountant implicitly agrees to perform a contract in a competent and professional manner.
C) An accountant who breaches his contract with a client may also be liable to a third party intended beneficiary.
D) All of these are correct.