A．By the end of this century．
B．By the first half of this century．
C．By the second half of this century．
D．In the middle of this century．

A．It is caused by stress from work or study．
B．It has a great impact on people's life．
C．It results in some strange diseases nowadays．
D．It gives people lots of trouble at work．

A．Talk about it．
B．Immerse ourselves in it．
C．Ignore it．
D．Shut it down．