—What do you think of the 3D-printed ______?—I’m afraid they are not safe enough to live in.
The Olympics ________ every four years. And the 29th Olympics ________ in Beijing in 2008.
I think ________ necessary ________ to take more exercise.
A football match ________ in our school next Monday.
We will spend our winter holiday in Shanghai, but we haven’t decided _______.
David visited lots of ________ in the world.