PETS－2语法讲解(28)
'感官动词 + doing/to do 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 gard...'
PETS－2语法讲解(27)
'begin(start) doing/to do begin/start to do sthbegin/start doing sth. 1)谈及一项长期活动或开始一种习惯时，使用doing.How old were you when you first started playing the piano?你几岁时开始弹钢琴？...'
