ONLINE SHOPPING

Câu hỏi: Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits end of the numbered blanks.
Online shopping is one of the fastest growing areas of the Net, offering users a large (26) _______of advantages over conventional shopping. Customers have access to a wider range of goods than in any shopping center; there are no queues or parking problems; "shops" are open 24 hours a day and purchases are delivered to your door. (27) _______, prices are competitive and online price comparison services enable you to find the best bargain. These sites search the Net for a (28) _______ and then show you how much different online stores are charging. Once you have decided what you are going to buy, and who you are going to buy it (29) _______, simply click on the "add to shopping basket" icon. If you change your mind later and decide not to make the purchase, you can always cancel your order. Select the "proceed to check out" icon when you have everything you want, give your payment details and wait for delivery, (30) _______ may take only a few day
The word or phrase which best fits the gap (30) is...
A. what
B. which
C. that
D. who