Every day, people come into contact with thousands of chemicals(化学品). These chemicals are said to be harmless to human health. In fact, the chemicals are considered so safe that we wash with them. We put them on our bodies and even our faces. Other chemical products are used throughout our homes.

    On its own, each chemical seems harmless. But in combination with other chemicals, they may become deadly. That is the finding of a two-year study by a group of scientists. The group was told to investigate the cancer-causing possibility of chemical mixtures.

    Linda Gulliver was one of 174 scientists on the group. Their job was to study the cancer-causing possibility of 85 chemicals. All 85 are said to be common in the environment.

Ms. Gulliver explains that chemicals have the ability, to form dangerous mixtures. Even simple minerals can become dangerous when mixed with chemicals found in plastics or beauty products.

    Working in groups, the scientists explored how different chemical mixtures could lead to cancer. Ms. Gulliver's team looked at the ability of different combinations to support the increase of malignant(恶性) human cells. She says the current way to identify whether chemicals cause cancer is to test them one at a time. This method leads to a long list of supposedly "safe" chemicals. She and her team say that approach needs to change.

    "We definitely need certain research ... to find out what mixtures of chemicals would be more harmful than others; what groups of chemicals, when together, would produce more harmful effects. And at the moment, that is not known."

    An estimated one in five cancers has been linked to chemical exposure. It may turn out that the cancer-causing villain (罪魁恶首)is not a single chemical at all. The villain could be a deadly combination. The increase of risk to cancer could be from exposure to many chemical compounds at the same time.

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1.Why do people use chemicals on their bodies?

A Because there are thousands of them.

B Because they think they are harmless.

C Because they need to wash themselves.

D Because they use them only at home.

解析：选B。B。细节理解题。由第一段可知，每天人们都在接触数以千计的日用化学品。而其中第2句告诉我们，这些化妆品据称是对人类无害。

2.The underlined word ‘investigate’ in paragraph 2 probably means____________.

A remove

B consider

C study

D discuss

解析：选C。C。词义猜测题。根据此词前后讲述，他们是在研究化学用品致癌的可能性，所以此词为：研究。

3.In what condition will common chemicals become dangerous?

A When they mix with other chemicals.

B When they have the ability.

C When they are found in plastics.

D When they are among the 85 chemicals.

解析：选A。A。细节理解题。由第二段可知，研究表明, 单个的化学品对人也许无害，但是当它们与其它化学品结合后就可能是致命的了，故选A。

4.Which was the one of the particular tasks of Ms. Gulliver’s team?

A To find which combinations support the increase of malignant human cells.

B To find how the chemicals combine into dangerous mixtures.

C To find out the long list of safe chemicals.

D To find the current way to identify whether chemicals cause cancer.

解析：选A。A。细节理解题。由第四段Ms. Gulliver's team looked at the ability of different combinations to support the increase of malignant human cells可知，他们关注那些化学物质的混合物对恶性人体细胞的增长所起的作用（A选项）。

5.The cancer-causing villain is a chemical combination____________.

A which is linked to chemical exposure

B which turns out to be single chemical

C which is the compound of many chemicals

D which produces harmful effect

解析：选D。D。词汇理解题。由文章最后两段可知，致癌的‘罪魁恶首’是致癌的化学混合物，这是对人体有更大影响的物质（D选项)。