混合題型
Tooth discoloration refers to the process of your teeth’s color becoming less white over time. If you are experiencing tooth discoloration, no harm done. It is a common process that occurs as humans age and affects only the surface of teeth. Nevertheless, unnatural discoloration can also happen. It is worth knowing that tooth discoloration can be prevented or, at the very least, controlled. To understand how to prevent this condition, we must first get to the bottom of the causes.
Broadly speaking, the causes of tooth discoloration can be divided into two categories: extrinsic and intrinsic causes. Extrinsic causes are factors coming from outside the body and are primarily food, drink, and tobacco. Common food and drink culprits include tea, coffee, red wine, chocolate, and blueberries. The deep colors of these items stick to the outer layer of teeth and can gradually cause staining if teeth are not cleaned well. Tobacco can lead to particularly severe staining. Nicotine and tar in tobacco are responsible for turning teeth into an unhealthy-looking brown or yellow. Research has revealed that generally, tooth discoloration is more prevalent among smokers than non-smokers.
Although the police were trying to get to the bottom of the case, they couldn't find any clues.
雖然警方試圖弄清該起案子,卻找不到任何線索。
Mr. Lin divided the class into two groups.
林老師把全班分成兩組。
Whatever I do, I stick to my principles.
不管做什麼事,我都會緊守原則。
Adults are responsible for their actions.
成年人要為自己的行為負責。
For me, singing at a KTV with friends is the best way to get rid of depression.
對我來說,和朋友去 KTV 唱歌是擺脫沮喪最好的方法。
Aspirin is very effective in relieving headaches.
阿司匹靈對緩解頭痛非常有效。