Questions 15 to 18 are based on the following dialogue happened in a bookstorE. Why didn‘t the man believe his eyes? 查看材料 A.Because he didn't know the pricE. B.Because he didn't see the price tag． C.Because medical texts are usually expensivE. D.Because the price is too high．
A.Why B.Because C. B.Because D. C.Because E. D.Because F.