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裡幹活了。(強調"我看見了"這個事實)
i saw him working in the garden yesterday.（強調"我見他正幹活"這個動作）
昨天我見他正在花園裡幹活。
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
答案a. 本題強調其動作，正在河邊玩，應此用see sb. doing sth句型。