29.

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

According to the meaning of the sentence "In some cases, it is necessary to make an appointment in advance, and it may take a small cost to drop or pick up some items." Here, the preceding and following sentences are in parallel structure, and A is correct.

Item B: Error, the meaning here is not "it will cost some money to drop or pick up the item", so you cannot use which to guide the attributive clause to modify the previous appointment.