---My dad bought me a new MP4, but I don't know ________.

---Let's read the instructions.

1. A.
   what to use
2. B.
   which one to use
3. C.
   how to use it
4. D.
   when to use it

--My dad bought me a new MP4, but I don’t know       。

--Let’s read the instructions．

A．what to use                                           B．which one to use

C．how to use it                                         D．when to use it