We were on the point of discussing financial investment_____ the telephone rang unexpectedly.

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

We were on the point of discussing financial investment_____ the telephone rang unexpectedly.

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

 We were on the point of discussing financial investment_____ the telephone rang unexpectedly.

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

We were on the point of discussing financial investment_____ the telephone rang unexpectedly.