A big earthquake __________7.1 on the Richter scale struck Yushu, knocking down buildings and causing more than two thousands people to lose their lives.
It is pretty well understood ________ controls the flow of carbon dioxide in and out the atmosphere today.
A plan has been put forward ________ more graduates should go to work in the country.
After three hours'climbing,they reached ________ they thought was the place they'd been dreaming of.
Engines are to machines ________ hearts are to animals.
The last time we had great fun was ________ we were visiting the Water Park.