钻削硬度较高的工件时，应选用（）的切削速度和较小进给量。
A.较大
B.较小
C.较低
D.较高
参考答案：C
What time does Jane ______ after school? [ ]
A. do her homework
B. does her homework
C. do her homeworks
D. does her homeworks
代谢性酸中毒常见的原因是（）
A.肺气肿、哮喘
B.肠瘘、肠梗阻
C.低钾血症
D.急性胃扩张
E.持续胃肠减压
