威特单体泵的润滑方式为（）
A.飞溅润滑
B.自然润滑
C.强制润滑
D.柴油润滑
参考答案：C
You really need to go out and get some fresh air and sunshine. You _______ overworked during the last
fortnight.[ ]
A. have been
B. were
C. had been
D. would be
下显示的是19世纪英国人口结构的变化状况，其中曲线①代表的阶级成份是
A．地主
B．资本家
C．工人
D．农民
