4. heavy 与thin
heavy和thin是一组意义相反的形容词，都可用来描述人的体型。heavy意为“胖的，笨重的”，比较级形式为heavier；thin意为“瘦的”，其比较级形式为thinner。例如：
He is very heavy, but his brother is thin.
他很胖，可他的哥哥却瘦。
【拓展】
heavy还可意为“重的；剧烈的；大的”等。例如：
heavy rain/snow/smoke大雨/大雪/浓烟
heavy smoker/drinker/eater烟瘾/酒瘾/食量大的人
have a heavy cold患重感冒
heavy(busy) traffic 交通拥挤
5. care about
care about意为“关心，在意”。例如：
She does not care about her husband at all.
她根本不关心她的丈夫。
Don't you care about this country’s future?
难道你不为国家前途担忧吗?
I don’t care about money. 我不看重钱。
【拓展】
care for意为“照顾，照料；想要；喜欢”。例如：
Would you care for some more tea? 想再喝点茶吗?
The mother cared for the sick child day and night.
母亲日夜照料着生病的孩子。
I don’t care for riding on a bike very much; I’d rather go on foot.
我不太喜欢骑自行车, 宁愿步行。
6. serious
serious作形容词，意为“严肃的、认真的、严重的、危险的”。比较级为more serious。常用搭配为：be serious about意为“对……认真”。例如：
How serious the matter is! 问题是多么严重啊！
I stopped laughing when I realized he was serious about it.
当我意识到他不是开玩笑时，我就不再笑了。
7. touch
(1)touch作动词，意为“感动；触摸”。例如：
Don’t touch the paint until it’s dry. 油漆未干,切勿触摸。
His sad story touched our hearts.
他的悲惨的故事深深打动了我们的心。
The peak seems to touch the sky. 山峰似乎已触及天空。
(2)touch作名词，意为“接触；联系”。例如：
The blind have a keen sense of touch. 盲人有敏锐的触觉。
They keep close touch with me. 他们和我保持密切联系。
8. reach
(1)reach作动词，意为“伸手；到达；抵达；取得联系”。例如：
He reached into his pocket to get his car keys.
他把手伸进口袋里拿车钥匙。
We reached the nearest railway station last night.
—The girl is helping her mother with the housework, isn’t she?
那个女孩正在帮妈妈做家务，不是吗？
—Yes, she is. 是的，她在帮。
—No, she isn’t. 不，她没有帮。
2. That’s why …
why引导的从句在此作is的表语，是表语从句。引导表语从句的词除了why外，还有that; whether; as if; what; which; who; whose; when; where; how等。表语从句与宾语从句一样，要求用陈述语序。例如：
That is where I was born. 那就是我出生的地方。
The problem is whether he will come. 问题是他是否回来。
This is what we need. 这就是我们所需要的。