--- You can use MSN to talk with Vivien on the Internet.

--- I know. But can you tell me ________?

-- You can use MSN to talk with Vivien on the Internet. 

--I know. But can you tell me ________?

1. A.
   when I can use it
2. B.
   what I can use it
3. C.
   why can I use it
4. D.
   how can I use it

--- You can use MSN to talk with Vivien on the Internet.

--- I know. But can you tell me ________?

A．when I can use it                                                B．what I can use it

C．why can I use it      D．how can I use it

-- You can use MSN to talk with Vivien on the Internet.
--- I know. But can you tell me ________?

--- You can use MSN to talk with Vivien on the Internet.
--- I know. But can you tell me ________?