Can you imagine_______such a mean person?
Stronger and more lasting memories are likely to be formed ________a person is relaxed.
Nearly four hundred supermarkets in Beijing are preparing to dim(使暗淡) their lights ________ the "Earth Hour 2010" on Saturday night.
A salty diet may increase the risk of stomach cancer ________ 10 percent, South Korean researchers found in a study of more than 2 million people.
The first textbooks ______ for teaching English as a foreign language came out in the 16th century.
Some people are worrying about the possibility ________ mobile phones could be responsible for a range of illnesses, from rashes(皮疹) to brain tumors.