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!

三角形连接时电动机的定子绕组有一组开路时，电动机转速降低，它的容量降低至原来的（）。

A.1/2

B.1/3

C.1/4

D.1/8