Once out of the earth’s gravity, the astronaut is____ by the problem of weightlessness.
Listen! Do you hear someone for help?
It was in the dining hall _______ was located behind the teaching building _______ I met her for the first time.
_______ to find the book from the library, she decided to turn to her professor for help.
The Voice of China has set up a stage _______ some people can achieve their dreams.
In Disneyland every year, some 800,000 plants are replaced because Disneyland refused to _______ signs asking his “guests” not to step on them.