当掌心向下平放在暗盒垂直投照时，显示的是以下哪项（）
A.拇指后前位
B.拇指侧位
C.拇指斜位
D.拇指前后位
E.拇指切线位
参考答案：C
安全门有几种手动打开方式？
请根据下面提示，写一篇短文，词数不少于50.
In your spoken Endlish class, your teacher shows you the following picture. You are asked to describe the picture and explain how you understand it.
