问题补充：
-- My brother bought me an iPhone 5, but I don’t know . Can you help me?
-- Let’s read the instructions.
A. what to use
B. how to use
C. what to use it
D. how to use it
答案：
A. what to use
B. how to use
C. what to use it
(答案→)D. how to use it
解析：本句的意思应该是“我不知道如何用它。”AB选项用what明显不对，因为用的就是iPhone5；另外，当用How时后面的动词应该有宾语。所以本题选D。
