柴油机喷油泵密封性的检查方法，普遍采用（）。
A．泵压法
B．透光法
C．自由下落法
D．煤油渗漏法
参考答案：A
若用同一显微镜观察同一标本4次，每次仅调整目镜或物镜和细准焦螺旋，结果得到下面各图。试问其中视野最暗的和物镜离装片最远的分别是[ ]
A．
B．
C．
D．
In the past I often wrote _____ my parents about my study at school, but now I e-mail them ____ rita@sunshinetown.com.cn or call them ______ 5551 6789 .
A．for; at; on
B．to; at; on
C．to; at; for
D．for; on; to
