【What are they drawing?】
What are they drawing?他们在画什么？
drawing 是draw 的分词形式，表示“画”，“拉”，draw 是一个不规则动词，过去式是drew .例如：
The boy can draw a house.
小孩会画房子。
Who drew the picture on the blackboard？
谁在黑板上画的画儿。
【I'm trying to draw a horse.】
I'm trying to draw a horse.我在试图画一匹马。
Try to do 表示“努力去做”。例如：
I'll try to study Chinese well.
我要尽力学好中文。
Are you trying to mend you kite?
你在试图修好你的风筝吗？
【Please don't play with my chalk.】
Please don't play with my chalk.请不要玩粉笔。
Play with 表示“玩耍”，play 后面直接跟一些运动球类或者乐器类表示参加这种运动或演奏这种乐器。
Don't play with fire.
不要玩火。
We are going to play basketball in the afternoon.
今天下午我们要去打蓝球。
The little girl plays piano（钢琴）very well.
小女孩钢琴演奏得很好。
【What was Li Lei drawing when the teacher came in?】
What was Li Leo drawing when the teacher came in?老师进来时，林涛正在画什么？
was drawing 是过去进行时。表示过去某一时间正在干某事，其构成形式是was（were）+现在分词。When …表示“当…时候”，when 在本句中起连词作用，引导出一个时间状语从句。例如：
I was reading a book at ten o'clock last night.
昨天晚上十点钟我正在读书。
What were you doing when I called you?
昨天我给你打电话的时候，你在干什么？
【He found it very difficult to get to sleep.】
He found it very difficult to get to sleep.他觉得很难入睡。句中的“find it +形容词+不定式”表示“发现干某事怎么怎么样”。不定式的内容就是指干某事的内容，但写在后面，而用it 代替不定式写在动词的后面，形容词作it 补语。例如：
I find it hard to finish the work today.
我发现今天难于完成工作。
I feel it very happy to work with you.
我感觉和你一起工作很幸福。
I think it important to have a walk after supper.
我觉得晚饭后散步很重要。
【He was just falling asleep when there was a loud knock at the door.】
He was just falling asleep when there was a loud knock at the door.他刚要入睡，突然就有人大声敲门。
was（were）doing …when（从句）….表示过去某一动作正在进行时，另一动作就开始了。例如：
I was walking in the street when I met a friend of mine.
我正在街上散步，这时就碰见一位朋友。
