______his son was ill,he felt very worried.

______his son was ill,he felt very worried.
A.Being known B.Knowing C.Known D.To know
选B 为什么

恩,是选B
这是ING形式作条件状语从句
动词的-ing形式既包括动名词又包括现在分词,在英语中使用极其广泛,同时也是高考中的重要考点,因此要求每位高中学生对其都应清楚了解并正确运用.下面就动词的-ing形式在句中做定语总结如下:
动词的-ing形式做定语在句中通常有两个位置,如果是单个的动词的-ing形式做定语,常放在被修饰词前做前置定语;如果是动词的-ing形式的短语做定语,常放在被修饰词后做后置定语.如:
1.He is an attacking player.他是一个攻击型的运动员.
2.He asked an embarrassing question.他提了一个令人难堪的问题.
3.A little child learning to walk often falls.学走路的小孩常常跌跤.
4.Do you know the number of people coming to the party?你知道来参加晚会的人数吗?
注意:当-ing形式做后置定语时,可以相当于相应的定语从句.如:
1.A young man writing novels came to speak to us yesterday.
→A young man who writes novels came to speak to us yesterday.
一位写小说的青年昨天来向我们作报告.
2.The girl sitting next to me was my cousin.
→The girl who was sitting next to me was my cousin.坐在我旁边的姑娘是我表妹.
-ing形式做定语通常从以下三方面考查,即:
1)说明被修饰词的性质,特征或用途.如:
1.They set up an operating table in a small temple.他们将手术台架设在一座小庙里.
2.He may be in the reading room,for all I know.他说不定在阅览室里.
3.Ladies and gentlemen,please go and wait in the meeting room.女士们先生们,请去会议室等待.
2)与被修饰词为主动关系且表示正在进行的动作.如:
1.There were about 200 children studying in the art school.有大约二百个孩子在这所艺术学校学习.
2.Who is the woman talking to our English teacher?
正在和我们英语老师谈话的那位妇女是谁?
3)有些-ing形式已经转化成形容词,常做定语用来修饰物,表示“令人……”.常用的此类词有:exciting,amusing,amazing,astonishing,shocking,puzzling,confusing,disappointing,discouraging,pleasing,striking,boring,tiring,touching,moving,interesting,satisfying,terrifying,frightening等.如:
1.That must have been a terrifying experience.那准时一段可怕的经历.
2.The experiment was an amazing success.那项试验是一个惊人的成功.
3.There is a page missing from this book.这本书缺了一页.
除了-ing形式能做定语外,如果-ing形式与被修饰词是被动关系,就用它的被动式,即being done.being doing通常表示正在被做,常做后置定语.如:
1.The tall building being built now is our new school.正在被建的高楼是我们的新学校.
2.The question being discussed was presented by the headmaster.正在被讨论的问题是被校长提出的.
ing形式的定义
ing形式包含传统语法的"动名词"和"现在分词"两种不同的概念.由动词原形加上-ing后缀而成的.和不定式一样也是一种非限定动词.ing形式具有动词的特征,同时也有名词和形容词的特征.

我们说ing形式是一种非限定动词是因为它不受到主语的人称、数和时的限制.

我们说ing形式具有动词的特征是因为：
它可以有自己的宾语,可以受副词的修饰等.

我们说ing形式具有名词的特征是因为：
它可以作主语、宾语和表语.

我们说ing形式具有形容词的特征是因为：
它可以作定语.