单项选择题

The relationship between exposure to ______ has not yet been determined.

A．ozone and fall in lung function
B．ozone and lung diseases such as asthma
C．nitrogen dioxide and worse lung function
D．smog and chronic bronchitis and emphysema

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热门试题

单项选择题

Figures showed that security screeners were ______ dangerous items.

A．able to detect
B．not able to detect
C．not effective in detecting
D．very effective in detecting

单项选择题

The sentence the seniors create a sense of meaning for themselves means the seniors ______.

A．acquire a new meaning of their lives
B．understand the meaning of the web
C．create a web site for themselves
D．add a new meaning to the web