问题详情：
单项选择
— How about buying an iPhone 4s for your mother’s birthday?
— Oh, maybe it’s too expensive, Dad. Do you know _______?
A. how much does it cost B. how much it costs
C. how much it cost D. how much did it cost
【回答】
B
【解析】本题是特殊疑问句作宾语从句，要用陈述句语序。故选B
知识点：宾语从句
题型：选择题
