I haven't seen Anna since she left our hometown two years ago, but we do keep in touch with each other by sending e-mails __________.
_______you study hard,you’ll succeed in time.
He tried his best to solve the problem,________difficult it was.
Measures have been taken to prevent the river from____.
Children often display an________curiosity about every new thing they encounter.
___________in reality,the story is popular with adults.