who speaks english best in your class?干吗用speaks?

问题描述:

who speaks english best in your class?干吗用speaks?

所以表示"说"的动词,talk, utter,speak等等,只有speak后面可以搭配english.
speaks,是因为who在这里是第三人称单数.

讲英语,动词用speak:
You speak very good English.
用英语说某个词或者某个句子,动词用say:Please say it in English.
从某种意义上来说,speak比say要正式一点,say多用于口语中,随便一点

因为在该特殊疑问句中,不知道who指的到底是单数还是复数,这时规定用第三人称单数形式,所以用speaks而不用speak.