When a buyer is in breach of a contract for the sale of goods, the seller may withhold delivery. Which of the following is true?
a. when the breach regarding one installment substantially impairs the value of the whole contract, all undelivered goods may be withheld
b. the seller who withholds delivery may not proceed with other remedies
c. the breach justifying withholding delivery of all undelivered goods need not go to the whole contract
d. withholding deliver is no longer available once goods are in the hands of a carrier even though the shipping term is FOB destination.