We were about to climb up to the top of the mountain ________ it began to rain heavily.

We were about to climb up to the top of the mountain ________ it began to rain heavily.

1. A.
   as
2. B.
   while
3. C.
   when
4. D.
   since

33. We were about to climb up to the top of the mountain ________ it began to rain heavily.

A. as                            B. while                C. when                D. Since

We were about to climb up to the top of the mountain ________ it began to rain heavily.

A. as                                     B. while                      C. when                      D. since