headmistress的复数形式怎么拼写？

The headmistress was an Oxford woman.女校长毕业于牛津大学。I was called to account for my conduct by the headmistress.我因为行为不检点而受到女校长的斥责.She is the deputy headmistress of the school.她是那所学校的代理校长....

headmistress的音标：headmistress的英式发音音标为：[ˌhed'mɑ:stə(r)]headmistress的美式发音音标为：['hɛdˌmɪstrɪs]...

n.女校长...