Question

Do you drink water that's been left sitting out overnight or even for another day? Have you noticed it tastes different?

Tap water that has been left to sit out slowly begins to acquire an off taste. Many people think that this is because of microorganisms(微生物). But that's not what makes old water taste not fresh. For that we can thank carbon dioxide. After about 12 hours, tap water starts to go flat as carbon dioxide in the air starts to mix with the water in the glass, lowering its pH and giving it an off taste. But it's most likely safe to drink.

However, back to those microorganisms. If you use a dirty glass day after day, there is more of a chance of bacteria making themselves known; a risk that increases if you share the glass with another mouth as well. But assuming you use a fresh glass every few days, you probably won't have a problem unless the glass has been touched by dirty fingers, and especially if those dirty fingers went unwashed after using the bathroom.

As for plastic water bottles that have been left out in the sun or in the car, step away from the bottle, warns Dr. Kellogg Schwab, director of the Johns Hopkins University Water Institute. "A chemical called bisphenol-A, or BPA, along with other things used to make plastic can leach(过滤) into your water if the bottle heats up or sits in the sun," he explains. BPA, as you probably know, has been linked to everything from heart disease to cancer. Schwab also adds that plastic used for commercial bottled water isn't meant to be washed or refilled, so use only one time and recycle. Or don't buy them at all; use refillable water bottles instead.

1.Tap water begin to acquire an off taste because of ________.

A. BPAB. the glassC. the microorganismD. carbon dioxide

2.According to Paragragh 2, tap water that's been left sitting out for 12 hours ________.

A. tastes betterB. is still safe to drink

C. contains few microorganismsD. is most likely undrinkable

3.What should we do with plastic water bottles that have been left out in the sun or in the car?

A. Throw them away.B. Refill them with fresh water.

C. Use them after they cool down.D. Clean them and use them again.

4.Which of the following is true about BPA?

A. It is safe for people to use.

B. It is a kind of new material.

C. It can cause great harm to people.

D. It is the main material to make plastic.

Answer

1.D

2.B

3.A

4.C

【解析】

1.D 细节理解题。根据文章第二段中But that's not what makes old water taste not fresh. For that we can thank carbon dioxide.可知，导致放的太久的水不新鲜的原因是二氧化碳。故选D。

2.B 细节理解题。根据第二段中After about 12 hours, tap water starts to go flat as carbon dioxide in the air starts to mix with the water in the glass, lowering its pH and giving it an off taste. But it's most likely safe to drink.可知，饮用水放置超过12小时喝起来还是健康的。故选B。

3.A 细节理解题。根据文章第四段的句子As for plastic water bottles that have been left out in the sun or in the car, step away from the bottle, warns Dr. Kellogg Schwab.可知，Dr. Kellogg Schwab警告我们要扔掉长期在阳光下或汽车里放置的塑料瓶。故选A。

4.C 细节理解题。根据最后一段的句子BPA, as you probably know, has been linked to everything from heart disease to cancer.可知，Dr. Kellogg Schwab指出BPA是一种与心脏病和癌症相关的化学物质，由此判断选C。