I often noticed the boy _school alone very soon.A leave B left C leaving D to leave

I often noticed the boy _school alone very soon.A leave B left C leaving D to leave
I often noticed the boy _school alone very soon.A leave B left C leaving D to leave

I often noticed the boy _school alone very soon.A leave B left C leaving D to leave
A
notice sb do sth
notice sb doing sth 看见动作,进行时

B和D的形式错误，至于C，这不是瞬间动作，所以C错

选A
B和D的形式错误，至于C，这不是瞬间动作，所以C错