英语阅读理解,具体看下面,如何做英语阅读理解

英语阅读理解,具体看下面,如何做英语阅读理解
Are you happy with your teeth?
In the last five years,teeth whitening has become very popular among young Americans.Now the trend(潮流)has come to China.If you turn on the TV you can see the Hong Kong pop star Karen Mok showing her bright white teeth,saying.“Want to be like me?Use white teeth strips(牙贴)!” You may even have decided to buy one.
But wait a minute.Dentists have something to say.They think that kids should not use whitening products until they are 1 6 or even older.
“We don’t know what will happen yet," says Dr.Nasrin Azim,a dentist in Chicago.“Studies have not been done on young people.I wouldn’t do teeth whitening on anyone under 18.”
The problem with whitening lies in the pulp(牙髓),the innermost(最深处的) part of the tooth.It has the tooth’s nerve ending.When we eat very hot or cold things,it’s the pulp that hurts.Kids have larger pulps.The larger pulp might make teeth more sensitive(敏感的) to whitening and get hurt.
Another problem is that the gums(牙床) around the teeth usually change shape with age.So if someone whitens his or her teeth during childhood,the darker,natural colour might show later around the gum line.At that time,your teeth will show two colours.And the darker colour is difficult to whiten.
The main focus of this article is on dental(牙齿的) ______.
A.care B.beauty C.cleaning D.illness
为什么很多人选C,如果光是因为这篇文章讲的是洁牙有关的方面就选C是不是有些片面,我这篇文章主要还是讲的为了保护我们的牙齿而不要去洁牙,我觉得应该选A,
还有为什么英语阅读理解的文意理解题我总是理解有偏差?应该怎样理解,只看表面还是看内涵.