After the equipment was introduced, they produced __________ machines this year as the year before.
| A．as twice many | B．as many twice |
| C．twice as many | D．twice many as |
Stronger and more lasting memories are likely to be formed ________a person is relaxed．
| A．where | B．unless | C．when | D．although |
Nearly four hundred supermarkets in Beijing are preparing to dim(使暗淡) their lights ________ the "Earth Hour 2010" on Saturday night．
| A．honor | B．honoring | C．to honor | D．having honored |
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．
| A．at | B．to | C．by | D．for |
The first textbooks ______ for teaching English as a foreign language came out in the 16th century.
| A．to be written | B．written | C．being written | D．having written |
Some people are worrying about the possibility ________ mobile phones could be responsible for a range of illnesses, from rashes(皮疹) to brain tumors．
| A．that | B．why | C．how | D．whether |