---- What’s the matter?

   ---- Oh, sorry. I pressed the button by chance and _______ the alarm clock.

  A. set out        B. send for       C. sent off         D. set off

---- What’s the matter? 

---- Oh, sorry. I pressed the button by chance and _______ the alarm clock.

1. A.
   set out
2. B.
   send for
3. C.
   sent off
4. D.
   set off