He's badly ill, ______ he is still working hard. [ ]
A. but
B. although
C. and
答案:A
猜谜语。
一口咬掉牛尾巴。
打一字:__________
边外注水适合于()油田。
A、大型
B、小型
C、边缘渗透率低
D、边缘渗透率高