All the following provisions are usually included in an insured stock cross-purchase buy-sell agreement EXCEPT:

A. A provision giving each surviving stockholder an option to buy a proportionate part of a deceaseds stock.

B.A provision establishing the purchase price to be paid for the stock of a deceased stockholder.

C. A provision committing each stockholder to buy and maintain life insurance on the other stockholders.

D. A provision permitting each surviving stockholder to buy from the estate of a deceased stockholder the life insurance the deceaseds estate owns on the life of each surviving stockholder.

Can you provide a detailed explanation for your answer? Please only answer if you have a strong background in estate planning.