In a secured transaction, the creditor's right to payment of a debt may be secured by his taking title to certain assets. In which one of the following types of transactions do those assets consist entirely of intangible property? a) A transaction under section 427 of the Bank Act, whereby a bank takes security over a farmer's growing crops with respect to a loan to purchase the seed and fertilizer necessary to grow those crops. b) A sale of goods in which the buyer will obtain title when he finishes paying the price in installments. c) chattel mortgage d) A debenture issued by a manufacturing firm with a floating charge over its inventory of products, e) assignment of book accounts