What happens if during a long and complex negotiation a buyer makes note of certain commitments made by the vendor, and the note was signed by both parties?

The most suitable answer is Option B. Is correct as they are bound by the contract only   

if a document is signed then it is a commitment ,  asigned contract is an obligation to all parties

My opinion is that the right answer is:

B. Is correct as they are bound by the contract only

Agree with MR  Muhammad Farooq 

Contract is the only authentic document between the parties.

Correct answer is B.

Thanks for invitation

A.  Is incorrect, as vendor is obliged to everything that was agreed

B is the answer,....

Thanks

Answer is B.

Any commitment not in the contract does not have to be met even though it was agreed upon during negotiations because contract supersedes all negotiations, discussions, memos, agreements etc. before signing the contract.

C.  Is insensitive and should accept this in view of long term relationship