I want to write to John, but I don't know ________.

1. A.
   what his e-mail address was
2. B.
   what is his e-mail address
3. C.
   what his e-mail address is
4. D.
   what was his e-mail address

I want to write to John, but I don’t know________ .

A. what his e-mail address was      

B. what is his e-mail address

C. what his e-mail address is        

D. what was his e-mail address