poker face的复数形式怎么拼写？

n.一本正经的面容，毫无表情的脸...

In business a poker face can be very useful.生意场上，不动声色会非常有用。She managed to keep a poker face.她一直努力板着脸。He wore a poker face during police questioning.在警察侦讯时,他一直面无表情....

poker face的音标：poker face的英式发音音标为：['pəʊkə feis]poker face的美式发音音标为：['pokɚ fes]...