ate knew
早期的人在他们知道如何使用火之前吃生肉谢了ben----- (see)them -----(run) when he-----(walk) homeben saw them running when he was walking home see sb doing sth 看到某人在做什么谢了when he ----(write)a letter to him,she---(come)when he was writing a letter to him, she came in 当他正在写信的时候他进来了