Why Is the Shareholder's Basis in the New Stock Received

Why is the shareholder's basis in the new stock received in a corporate reorganization the value of the stock received less the postponed gain?

A) This ensures that the basis is the value of the stock given up in the reorganization.
B) The realized gain is the amount that would be recognized if the stock was sold outright. This gain may not be recognized, however, unless there is boot.
C) The basis is the vehicle to ensure that the gain postponed will be recognized in the future when the stock is sold.
D) A carryover basis or a substituted basis will not include the postponed gain that is necessary in a tax-deferred transaction such as a reorganization.
E) All the above statements are true.