It is uncertain ___________ side effect the medicine will bring about，although about two thousand patients have taken it.
| A．that |
| B．what |
| C．how |
| D．whether |
A wild Siberian tiger has been caught on camera in Heilongjiang Province, __________ the first images of this sort were captured．
| A．which | B．when | C．where | D．that |
Words failed me when I heard the news of the New Year‘s Eve stampede in Shanghai． But for lacking a sense of safety, so many people __________ killed or injured．
| A．couldn‘t be | B．wouldn‘t have been |
| C．mustn‘t have been | D．shouldn‘t be |
Our nation should first develop modern law __________ in ruling the country by law．
| A．awareness | B．opportunities |
| C．regulation | D．principle |
__________ on Wechat is a common phenomenon, and more people hardly write letters．
| A．Communicate | B．Communicated |
| C．To communicate | D．Communicating |
People are __________ shoppers in China on November 11th, contributing to more than 35 billion online shopping sales．
| A．potential | B．enthusiastic |
| C．intelligent | D．temporary |