_______ how to do the homework, I went to ask my teacher for help.
| A．Not to know | B．Not knowing | C．Knowing not | D．Not known |
_______ is very important for us students to learn English well.
| A．It | B．As | C．What | D．There |
You’d better________ your scores and see if you have passed the exam.
| A．add up to | B．add to | C．add | D．add in |
How did all these _________?
| A．came out | B．come up | C．come across | D．come about |
They lived a hard life and were often made _______ for over ten hours a day.
| A．work | B．to work | C．to working | D．worked |
_____ of the students who took part in the military training is 450.
| A．A number | B．A lot | C．Lots | D．The number |