There are many factors that _________ the popularity of the 3G cell phone．Higher speed of surfing the Internet is one．
| A．answer for | B．provide for |
| C．account for | D．apply for |
They travelled around _____ Changchun by _____ bus.
| A．the, / | B．/ , a | C．/, / | D．the, a |
John rushed out in a hurry, _____ the door _____ .
| A．leaving; unlocked | B．leaving; unlocking |
| C．left; unlocked | D．left; unlocking |
Please come to visit me if _________________.
| A．you are convenient | B．it is convenient of you |
| C．you are for convenience | D．it is convenient for you |
---Why do you look so sad?
---There are so many problems_______.
| A．remaining to settle | B．remained settling |
| C．remaining to be settled | D．remained to be settled |
Even the __________ doctor couldn’t cure him __________ his deadly disease.
| A．experience; of | B．experienced; of |
| C．experience; with | D．experienced; with |