________ they become dirty, the lakes are not able to clean themselves
| A．Once | B．Since | C．As | D．Because |
There is a 20-minute parking ________here, so we must get back to the car very quickly.
| A．freedom | B．limit | C．allowance | D．ability |
But for the help of my English teacher, I _______ the first prize in the English Writing Competition.
| A．would not win | B．could not win | C．could have won | D．would not have won |
This monument was built ______ the little hero.
| A．in place of | B．in search of | C．in memory of | D．in need of |
—Do you mind if I keep pets in this building?
— _______ .
| A．I'd rather you didn't, actually. | B．Of course not, it's not allowed here. |
| C．Great! I love pets. | D．No, you can't. |
—I didn’t go to work yesterday afternoon because my car broke down.
—You _______ mine. I was not using it.
| A．might borrow | B．could have borrowed | C．can have borrowed | D．ought to have |