—Have you heard that George quit his job?—Yeah, but I can't________why he did so.
Mary never does any reading in the evening ,______.
Maybe you have been to many countries , but nowhere else ___such a beautiful palace.
I failed in the examination last term and only then ____ the importance of studies.
Only when your identity has been checked , _________.
The old couple married for 40 years and never once____ with each other.