如图为一种电磁制动器示意图，图中代号7表示的是（）。
A、制动弹簧
B、限位螺钉
C、铁心
D、制动轮
参考答案：D
请看录像，找出录像中秘书行为及工作环境中的至少处正确或错误的地方。
An analyst does research about common probability. A return distribution has a mean of 1.8% and a variance of 2.25. If returns are normally distributed, the probability of observing a return value less than -1.2% is closest to:（）
A. 1.0%
B. 2.5%
C. 5%
