It may be necessary to stop _____ in the learning process and go back to the difficult points in the lessons．
| A．at intervals | B．at random |
| C．at ease | D．at length |
Not everybody knows exercising too much can_________ serious pain and even injuries.
| A．attach to | B．attend to |
| C．contribute to | D．devote to |
—Jane looks down today, what’s up?
—Well, ________happened between Jane and me is none of your business.
| A．whichever | B．whatever |
| C．no matter which | D．no matter what |
All his hard work finally ________ in the summer of 2014, when he was admitted to his dream university.
| A．took off | B．ran off |
| C．set off | D．paid off |
How much cheaper do you think a flat in the countryside is than ______ in the downtown?
| A．one | B．it | C．that | D．those |
How long do you think ______ the Microsoft brings out a new product?
| A．it will be before | B．will it be until |
| C．will it be when | D．it will be that |