Mark was a student at this university from 1999 to 2003, _______he studied very hard and was made Chairman of the Students’ Union.
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.
It’s helpful to put children in a situation___________they can see themselves differently.