13、Essentially, a theory is an abstract, symbolic representation of what is conceived to be reality.
理论在本质上是一个被构想成现实的抽象和符号性象征的表达。
主句：a theory is an abstract
主句主语：a theory
主句系动词：is
主句表语：an abstract ，symbolic representation
What引导的定语从句，修饰abstract 和representation ：what is conceived to be reality.
从句谓语：is conceived 一般现在时的被动语态
从句宾语：to be reality
symbolic 作定语修饰representation 意为“符号表示”
to be reality介词短语做宾语，意为“成现实”
14、Long before children are able to speak or understand a language, they communicate through facial expressions and by making noises.
儿童在能说或能听懂语言之前 很久就会通过面部表情和靠发出噪声来与人交流了。
分析：前半句
主语：children
系动词：are
表语：able
状语：to speak or understand a language
Be able to：“能够;（因具有品质或技能）能做到…的;（因有足够的自由、权力、时间、财力等而）可以…的”
例：doubt they'll be able to help but it's worth a try.
我不敢肯定他们能够帮得上忙，但不妨试一试。
后半句：
主语：they
谓语：communicate
宾语：through facial expressions and by making noises
Through和by都是介词，表示“通过”
介词by后用动名词形式，making 表示“制造噪音”
相关语法：Be able to 和 can的不同点：
1、can只有两种时态, 即can 和could, 而be able to 有多种时态, 如was/were able to, will/shall be able to, have/has been able to等例：I’ll be able to drive the car in a week.我一周内就能开车了。
He couldn't answer the question.他没有能回答那个问题。
2、表示过去通过努力终于做成了某事要用be able to，而不能用can。
例：I was able to swim to the bank after the boat turned over.船翻了之后，我才游到岸边。
3、can能表猜测，be able to不能。can的这种用法主要用于疑问句和否定句。
例：Somebody is knocking at the door. Who can it be?有人在敲门。会是谁呢?
It can’t be our teacher who is knocking at the door.不可能是我们的老师在敲门。
4、can 可以表 “允许”, 与may可以互换, 此时不能用be able to 代替。例：“Can / May I sit here？”“Yes, please.”
5、can 是情态动词，只能用作谓语成分，be able to是普通动词短语，既可以作谓语，也可以作非谓语。
例：Being able to speak English fluently, he has no difficulty in communicating with the Americans at the party.
他英语说得很流利，在聚会上与美国人交流没有困难。How I long to be able to communicate with the foreigners in fluent English!我多么渴望能用流利的英语与外国人交流啊!
6、be able to 后边接动词不定式表示一种实际情况时，其否定形式不是be not able to，而是cannot。例：Were you able to catch the first bus yesterday morning?No, I couldn’t.你昨天早上能赶上头班车吗?
7、 一般说来, be able to 后边的动词不定式没有被动语态。例：I’m sure he is able to correct his mistakes in grammar.我相信他能改正语法错误。
错误: I’m sure his mistakes are able to be corrected by him.
Be able to 和 can的相同点：
can 和be able to 都可以表示能力.can泛指一般的能力,而且只有两种形式,即:can, could．
be able to 则主要指具体做到了某件事的能力，其形式主要是靠be 发生变化，所以形式比can 多．
可以说：I can swim. I am able to swim.
但是不能说：All the people could escape from the big fire in time.
只能说：All the people were able to escape from the fire in time.
