常见的血循环毒类毒蛇有（）
A.五步蛇
B.海蛇
C.银环蛇
D.烙铁头
E.金环蛇
参考答案：A, D
肺性脑病时，PaCO2一般应大于（）
A.60mmHg
B.65mmHg
C.70mmHg
D.45mmHg
E.50mmHg
My father is a little lazy. He _____ very hard.[ ]
A. don't work
B. don't works
C. doesn't work
D. doesn't works
