Recognising broad categories of images is one of the general problems that computers are not______.

A．It increased the students’ white blood cell.
B．It increased some students’ energy level.
C．It improved the students’ ability to play musical instruments.
D．It released a natural painkiller in some students’ bodies.

A．The man should go and enjoy the performance.
B．The man could play games on the Internet.
C．The man should go to bed early.
D．The man can enjoy the performance without going out.