When all or part of an order cannot be processed because the merchandise is temporarily out of stock or has been discontinued，which of the followings should not be done？（）

A.Express appreciation for the order and identify it by the customer's order number or by date if the order is unnumbered.
B.Express regret that either all or some identified items cannot be shipped and state the reason.
C.Give a guarantee to the customer that the items will be shipped in time.
D.If one or more items have been discontinued，suggest an alternative for the customer.