ask 问 ask sb 问某人 ask a question 问问题
say 说 say sth 说某事
tell 讲述 tell a story 讲故事 tell sb sth = tell sth to sb 告诉某人某事 tell on sb 告发某人
speak 讲 speak a language 讲一种语言 speak in English/Chinese
区分的方法就是记住每个单词的固定搭配.