Although the causes of cancer ________, we do not yet have any practical way to prevent it．
| A．have uncovered | B．have been uncovering |
| C．are uncovering | D．are being uncovered |
Each time I________a good essay when reading newspapers，I cut it out and keep it.
| A．work out | B．come across |
| C．care about | D．put down |
To their disappointment，Dr Wang gave a speech about the economy without even a passing________to the problem of unemployment.
| A．connection | B．appointment |
| C．reference | D．exploration |
According to the arrangement，the athletes of our school________at the gym for two hours every day.
| A．work out | B．carry out |
| C．take in | D．set aside |
—You look tired，Mike.
—Oh，I stayed up last night，________the final of the Voice of China on TV.
| A．watched | B．having watched |
| C．watching | D．watch |
A recent survey shows the number of people who shop in stores________，while far more are shopping online.
| A．decrease | B．decreases |
| C．is decreasing | D．are decreasing |