问题补充：
---Look at those shoes, Mike!
---Wow! They look very cool, but I wonder .
A. how much are they
B. how much do they cost
C. if my parents will buy them for me
D. that my parents will buy them for me
答案：
A. how much are they
B. how much do they cost
(答案→)C. if my parents will buy them for me
D. that my parents will buy them for me
解析：if既可以引导宾语从句又可以引导状语从句。if充当宾语从句的连接词时，相当于whether，词义为“是否”，遵循宾语从句的时态规则，可根据语境选择任何时态；
