She says the current way to identify whether chemicals cause cancer is to test them one at a time. This method leads, she adds, 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.”

　　本文讲述的是一种新的发现：单独看来无害的化学物质，可能与另一物质产生化学反应并会产生致癌物质。这项研究会不断地进行下去。

　　5．The purpose of the researchers' work is ________.

　　A．to find ways to protect human cells

　　B．to study the character of the chemicals

　　C．to study the cancer－causing possibility of mixtures

　　D．to study how deadly the chemicals in our homes are

　　答案：C　细节理解题。根据第三段的描述可知，研究的对象是造成癌症的可能的混合物。

　　6．According to Ms Gulliver's words, their research work is ________.

　　A．still limited

　　B．completely successful

　　C．practical to other researchers

　　D．not well received

　　答案：A　推理判断题。根据第六段和第七段Ms Gulliver所说的话可以判断对这些物质的不确定性，因而可推知答案是A。

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