While it is essential that the text covers the subject adequately, it is also important that it is neither too detailed or too complex for the intended reader.

A．for

B．nor

C．no

D．not

鉴于近年来自然灾害频发，各省应充分考虑重大灾害、电源故障，制定（）的容灾备份方案，即至少满足主用设备和备用设备物理上不在同一个机房或同一通信楼，有条件的情况下，考虑跨区域容灾。

A.跨区域、跨单位

B.跨市级、跨省级

C.跨机房、跨区域

D.跨区域、跨空间