While sleeping, some water mammals tend to keep half awake in order to ________.
A) alert themselves to the approaching enemy
B) emerge from water now and then to breathe
C) be sensitive to the ever changing environment
D) avoid being swept away by rapid currents
A. wreckage B. foundation C. base D. destruction
The international situation has been growing ________ difficult for the last few years.
A) invariably B) presumably C) increasingly D) dominantly
