—When did your school hold the sports meet?—Last week. And I _______ the girls’ 400-metre race.
We can’t do two things _____.
Jim’s shirt is made _____ silk , and it’s made ______ china.
No smoking, please. It’s ____ the rules.
Although we are young, ______ we can still do something to help them.
It is necessary _____ something to protect our environment.