—Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
The audience when they watched his funny performance.
Every day we are using so many raw materials which _________that they _________.
_______the fierce competition in finding a good job in big cities, many fresh graduates are still trying their fortune in Beijing.
______ the Internet is of great help, I don’t think it is a good idea to spend too much time on it.
The first World Cities Day of the UN, _______on Oct.31, 2014 in Shanghai, focused on leading urban transformation.