The organization has introduced the so called "demountable structures" into London games,

The organization has introduced the so called "demountable structures" into London games, what do "demountable structures" mean？

A．They are structures like mountains which are hard to move around.

B．They represent a long history of London.

C．They can be taken down and moved to some other part of the country and put back up again.

D．They are new facilities against bad weather.

请帮忙给出正确答案和分析，谢谢！