The dentist has been telling you for years: brush your teeth twice a day; one time in the morning and one time in the evening. Most people feel like it would be better to brush their teeth after breakfast because they don’t want to walk around with bits of breakfast stuck in their teeth.

Surely, it is especially significant to brush your teeth in the morning. That way, you can take away the bacteria (细菌) that have been building up during the night while you were sleeping. And it is always nice to start your day with fresh, minty (薄荷味的) breath. But the dentist doesn’t say anything about the exact time of day. So, when should you actually brush your teeth? Before, or after you eat your food?

As it turns out,    ▲   . Surprising, right? When you brush your teeth after you eat something, you could damage your teeth, especially after eating something sweet or sour. When you brush right after eating something sweet or sour, you could damage your tooth enamel (釉质). And that increases your risk of getting a cavity (蛀牙).

So, if you don’t want to brush before eating breakfast but you really want to leave the house with fresh breath, then wait thirty minutes after eating before brushing. That is much safer for your teeth! And if you’re in a rush, you can use mouth wash instead.

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1.What do most people do?

A They never brush their teeth in the morning.

B They brush their teeth twice in the evening.

C They brush their teeth after breakfast.

D They walk around without having breakfast.

解析：选C。C 细节理解题。根据第一段的“Most people feel like it would be better to brush their teeth after breakfast...”可知，很多人在吃早餐后刷牙。故选C。

2.What does the writer think of brushing teeth in the morning?

A It’s unnecessary.

B It’s important.

C It’s popular.

D It’s comfortable.

解析：选B。B 细节理解题。根据第二段第一、二句“Surely, it is especially significant to brush your teeth in the morning. That way, you can take away the bacteria...”可知，作者认为早上刷牙很重要，因为那样可以清除口腔里的细菌。故选B。

3.Which can be put back into the “ ▲ ”?

A it is better to brush your teeth before breakfast

B you’d better never brush teeth before eating food

C it is good to brush your teeth after breakfast

D it’s better never to brush teeth after eating sweets

解析：选A。A 推理判断题。结合第三段空白处后文描述了吃早饭后刷牙可能带来的坏处：损伤你的牙齿，尤其是当你吃完甜食或者酸性食物马上就去刷牙，可能会损伤牙釉质，增加患蛀牙的风险。由此判断，结果证明是，吃早餐前刷牙更好。故选A。

4.Why should we wait half hour after eating before brushing?

A To not be in a hurry.

B To brush teeth better.

C To have fresh breath.

D To protect our teeth.

解析：选D。D 细节理解题。根据最后一段中的“then wait thirty minutes after eating before brushing. That is much safer for your teeth”可知，吃早餐后等30分钟再刷牙对我们的牙齿更安全，即等30分钟是为了保护我们的牙齿。故选D。

5.In which part of a magazine can we read the passage?

A Health.

B Food.

C Science.

D Culture.

解析：选A。A 推理判断题。本文主要描述了保护牙齿的相关内容，与健康有关。故选A。