One day I was dining with my friend Zhou in McDonald when two young girls came in hand in hand. While enjoyed a hamburger, I found Zhou looking around at something strangely.

I raised my eyes to see what was happening. The two girls are making gestures skillfully. Obviously they were deaf-mutes. I had learned some sign languages ago, so I showed various gestures with Zhou following me in low spirits. We played and laughed cheerfully as if there had no one else present. Suddenly we saw both the two girls glaring at us. Before we could explain to them, they had walked out angrily, left the food unfinished. They thought we were making joke of them. How I regretted!

调整最后传动齿轮时，如将盆形齿轮移向角尺齿轮，此移动将使齿轮之接触位置移向（）

A.盆形齿轮之齿腹

B.盆形齿轮之齿顶

C.盆形齿轮之齿跟

D.盆形齿轮之齿尖