We may find that learning a foreign language does not have to be________learning our mother tongue,but can in fact be twice ________.
Can you believe that in ___ a rich country should be ___ many poor people?
Mis Smith is a friens of ___.
--Has the train arrived yet?---No, it ought to ___ twenty minutes ago.
I didn't expect that so many people ___ to join in the work.
Mr.Brown ___ goes to bed before midnight.