单项选择题
The rat has many enemies and its greatest enemy is man. Nevertheless, it is the survivor. Although man has (16) an unending war against them, rats have (17) the world. In almost every country, from the (18) cold of the Arctic regions to the unbearable (19) of the tropics, rats are (20) thriving, increasing and multiplying.
18()
A.freezing
B.mild
C.frigid
D.mounting