B. 动名词 (doing)本质上是名词属性，指代一个活动、一件事情或者一项功能，同时具备动词的特性。作宾语时，一般表示做过某事，正在做某事或与谓语动作同时进行。动名词可充当主语、宾语、介词宾语、表语、宾语补足语、定语或同位语等。
a.动名词充当主语。
如：Watching TV too muchisbad for your eyes.
看电视太多对眼睛不好。
b.动名词充当表语。
如：His hobby is playing basketball. 他的爱好是打篮球。
c.动名词充当宾语。
如：She has to finish doing her homework now.现在，她不得不完成作业。
I will never give up doing sports. 我永远不会放弃运动。
You should try eating more fruit.
c.动名词充当介词宾语。
如：What about eating out? 出去吃饭怎么样？
She is good at swimming. 她擅长游泳。
d.动名词充当宾语补足语。
如：Would you mind me sitting here?你介意我坐在这里吗？
We call this action cheating. 我们称这种行为为作弊。
e.动名词充当同位语。
如：That is her habit, listening to music before going to bed.
那是她的习惯，睡前听音乐。
f.动名词充当定语。
如：I have to take a dancinglessonlater. 稍后我要上舞蹈课。
C. 现在分词(doing) 作为非谓语动词，不可与be动词连用。但依然保持现在分词的动词属性，可以和自己的宾语或状语构成分词短语，表示主动或进行的含义。可充当宾语补足语，伴随状语或定语。
a.单个现在分词充当定语。
如：The dancinggirl is Tom's girlfriend.
正在跳舞的女孩是汤姆的女朋友。
b.现在分词短语充当后置定语。
如：I don't know the man smoking at the door.
我不认识在门口吸烟的那位男子。
c.现在分词充当宾语补足语。
如：I heard someone crying out for help.我听见有人呼救。
He always keeps me waiting so long. 他老是让我等很久。
d.现在分词充当伴随状语。
如：They had fun fishing in the lakelast Sunday.
他们上周日在湖里钓鱼很愉快。
He hurt himself playing footballyesterday. 他昨天踢足球时受伤了。
I had trouble learning to dance. 我学跳舞时遇到了困难。
Tom is comfortable speaking Chinese now.
现在，汤姆说中文已经很流利了。
