--- Did you turn off the lights before you left the computer room?

   ---- Oh, I forget _______ them off. I’ll go to do it.

   A. to turn    B. having been turned C. to have turned  D. turning

----The light in the office is still on. ----Oh, I forget ______.

 —What’s the noise?   —Oh, I forget to tell you. The new machine      .

A. has been tested           B. is tested             C. will be tested    D. is being tested

    ----The light in the office is still on.

----Oh, I forget ______.

---The light in the office is still on. 

---Oh, I forget ______.

1. A.
   turning it off
2. B.
   to turn it off
3. C.
   turning off it
4. D.
   to turn off it