在老年冠心病的一级预防中被提到的首位药物是（）
A.硝酸酯类
B.降脂剂
C.钙离子拮抗剂
D.阿司匹林
E.血管紧张素转换酶抑制剂
参考答案：D
Ever since he caught the N1H1, Peter _____ so much pain that he is coughing day and night.[ ]
A. suffered from
B. has suffered from
C. suffers from
D. were suffering from
推油门手柄时，带柔性回输的闭环转速控制系统的工作过程有那几个阶段？每个阶段的特点是什么？
