Allan is old enough to go to work. 艾伦到上班年龄了。
2. Because about one fifth of the air is made up of oxygen, the water rises and fills about one fifth of the jar. 句式be made up of意为“由组成”，后加名词或代词作介词宾语。
This grade is made up of ten classes. 这个年级是由十个班组成的。
句中的one-fifth意思是“五分之一”，这是一个分数。分数的表达一般遵循以下规则分子用基数词，分母用序数词；
当分子大于一时，分母要用复数形式；
并且其中的连字符号有时可以不要。
one-fourth 四分之一 three fifths 五分之三 3. Maybe Brian and I can join you after supper. 动词join在这里表示“加入”，如果表示“加入到某人的某种活动中”可用句式join somebody in 。
Lisa, can you join us in the game 丽萨，你能和我们一起做游戏吗 4. Fantastic facts about the butterfly have been drawing Dr. Taylor’s attention. 句中的have been drawing 是现在完成进行时，它由“助动词 have has been 现在分词”构成，当主语是第三人称单数时用助动词has，其他情况用助动词have。现在完成进行时主要表示从过去开始一直持续到现在的动作，这个动作是否延续下去，要根据上下文而定。它往往与表示一段时间的时间状语连用，如all the time, this month, all day, these few days, for a year, since a week ago等。
She has been playing basketball after school this week. 这个星期她放学后一直打篮球。
Tony has been drawing in his bedroom all the afternoon. 托尼在卧室画了一下午。
5. This is both puzzling and interesting for many scientists. 连词bothand的意思是“和都，既也”，它可以连接句中句子成分相同的词语，如果用它连接主语时，谓语动词要用复数形式。
She likes both sports and music. 她既喜欢运动，又喜欢音乐。
Both Li Ping and her mother take rcise every morning. 李萍和她妈妈每天早晨都进行锻炼。
6. But building a living thing is far more complex than building a house. 比较级前可以用much, even, still, far, a bit, a little, a lot 等词加以修饰。
This unit is much easier than that one. 这个单元比那个单元容易得多。
This book is far more interesting than that one.这本书比那本书有趣得多。
7. Scientific discoveries are making our lives better and better. “比较级 and 比较级”表示“越来越”。
My sister is growing taller and taller. 我妹妹长得越来越高 Our city is becoming more and more beautiful. 我们的城市变得越来越美了。