I wonder________there are so many natural disasters across the world in 2010.
| A．which it is that | B．what is it that |
| C．how it is that | D．why it is that |
White-collar workers in China are willing to postpone their retirement age ______ blue-collar workers prefer to retire early.
| A．when | B．while | C．though | D．since |
“Got it?” Professor Smith says, “______, let’s move on to the next part.”
| A．If not | B．If anything | C．If ever | D．If so |
By accepting lower prices, organizers can sell tickets that would ______ go unsold.
| A．therefore | B．otherwise |
| C．instead | D．however |
The lack of health facilities and necessary protection for medical workers partly ______ the epidemic (蔓延) of Ebola.
| A．accounted for | B．headed for |
| C．called for | D．sent for |
Dozens of people were waiting with a camera for ______ seemed like hours, hoping to catch a glimpse of the US First Lady, Michelle Obama.
| A．that | B．when | C．which | D．what |