单项选择题

What steps could be taken to improve the air

A．Reduce the amount of nitrogen.
B．Increase the release of oxygen.
C．Reduce nitrous oxide emissions.
D．Stop industrial activities.
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单项选择题
Who sponsored the conference on population
A．Cairo.
B．The United Nations.
C．The World Bank.
D．The World Health Organization.
单项选择题
The party was held________.
A．at Jane’’s house
B．at Jane’’s aunt’’s house
C．at Jane’’s sister’’s house
D．at Jane’’s brother’’s house
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