No one has yet succeeded in solving the _____ of how life first began.
| A．biology | B．gravity | C．puzzle | D．theory |
The policeman said the accident was __________ careless driving. Therefore, the driver had to pay for all the losses.
| A．due to | B．thanks to |
| C．led to | D．owe to |
__________ their timely help, we overcame the difficulties at last.
| A．Thanks to | B．Thanks for | C．As a result | D．Because |
Eating too much fat can __________ heart disease I and cause high blood pressure.
| A．attend to | B．devote to |
| C．distribute to | D．contribute to |
The river near our school has become clean again as new measures have been __________ to prevent it __________ any further.
| A．taken; polluting |
| B．taking; being polluted |
| C．taken; being polluted |
| D．taking; to be polluted |
In some countries packets of cigarettes come with a government health warning __________ to them.
| A．appealed | B．applied | C．appointed | D．attached |