____________ to do the repair, and what you need is only a hammer and some nails.

A．It is hard

B．That is easy

C．That is hard

D．It is easy

野炊结束后，同学们及时用沙土盖灭火堆，其主要灭火原理是

A．将可燃物与氧气隔绝

B．撤离可燃物

C．降低可燃物的着火点

D．降低可燃物的温度