我的工作是教顾客怎样用电脑.Translate it into English

题目

我的工作是教顾客怎样用电脑.Translate it into English
Please provide a better answer and explain it into English.
What is the difference among (1),(2),(3),(4）,(5),(6),and (7)?
1)My job duty is to teach customer how do use computer.
2)My job duty is to teach customer how touse computer.
3)My job duty is to teach customer use computer.
4)My job duty is to teach customer computer.
5)My job duty is to teach customer using computer.
6)My job duty is teaching customer how to use computer.
7)My job duty is teaching customer how do use computer.

答案

答案是6　,　因为答案比较完整~