感官动词 see,watch,observe,notice,look at,hear,listen to,smell,taste,feel + do 表示动作的完整性,真实性；+doing 表示动作的连续性,进行性
I saw him work in the garden yesterday.
昨天我看见他在花园里干活了.(强调"我看见了"这个事实)
I saw him working in the garden yesterday.（强调"我见他正干活"这个动作）
昨天我见他正在花园里干活.
典型例题
1）They knew her very well.They had seen her ___ up from childhood.
A.grow B.grew C.was growing D.to grow
答案：A.因题意为,他们看着她长大,因此强调的是成长的过程,而非正在长的动作,因此用see sb do sth 的句型.
2）The missing boy was last seen ___ near the river.
A.playing B.to be playing C.play D.to play
答案A.本题强调其动作,正在河边玩,应此用see sb.doing sth句型.