Keys should never be hidden around the house since thieves _____ know where to look.
We ________ contact with each other for years. And last week we ________ contact again.
The hotel wanted to charge $150 for the room service, but we couldn't ____________ to live in such an expensive hotel.
As is reported, it is 100 years________ Qinghua University was founded.
—What a mistake! —Yes. I________his doing it another way, but without success.
________students are required to take part in the boat race.