Although police could be seen everywhere, they seemed to be searching the houses almost ________.[ ]

A. at ease

B. at random

C. at risk

D. at length

在列出的各省市中，保险密度和保险深度最低的分别是( )。

A．青海和湖南

B．河南和青海

C．贵州和青海

D．甘肃和山东