I felt somewhat disappointed and was about to leave, ________ something occurred which attracted my attention.

1. A.
   unless
2. B.
   until
3. C.
   when
4. D.
   while

I felt somewhat disappointed and was about to leave _____ something occurred which attracted my attention.

A. unless B. until   C. when  D. while

I felt somewhat disappointed and was about to leave _____ something occurred which attracted my attention.

    A. unless       B. until           C. when         D. while

 I felt somewhat disappointed and was about to leave, ___ something occurred which attracted my attention.

  A. unless            B. until           C. when           D. where

I felt somewhat disappointed and was about to leave _____ something occurred which attracted my attention．

A．unless        B．until         C．when         D．while