He always has a lot of______ideas in his mind, and sometimes we do not even know what he is thinking about.

A．Hydroponics is a new development in agriculture.
B．Malthus’ prediction has been proved to be correct by modern experts.
C．Hydroponics may be the answer to the world food shortage in the future.
D．Conventional methods of agriculture should be improved to step up food production by two per cent every year.

A．domestic
B．devilish
C．unusual
D．civilian