感官動詞 see, watch, observe, notice, look at, hear, listen to, smell, taste, feel + do 表示動作的完整性，真實性;+doing 表示動作的連續性，進行性

I saw him work in the garden yesterday.

昨天我看見他在花園里干活了。(強調"我看見了"這個事實)

I saw him working in the garden yesterday.(強調"我見他正干活"這個動作)

昨天我見他正在花園里干活。

典型例題

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。因題意為，他們看著她長大，因此強調的是成長的過程，而非正在長的動作，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 playingC. playD. to play

相關內容：

省to 的動詞不定式

動詞不定式的否定式

語法：名詞性wh-從句