did you notice someone (step)on the grass just now.为什么不是stepping
问题描述：
did you notice someone (step)on the grass just now.为什么不是stepping
答
根据题面意思,是在问,有没有注意到什么人刚才在踩踏草坪.
如果用stepping,看例句.
They notices someone stepping on the grass.
他们注意到有个人正在踩踏草坪.