Last summer I visited the People’s Great Hall, in __________ many important meetings are held every year.
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China is a country ______ has a long history.
A. which
B. where
The first place _________ they visited in London was the Big Ben.
A. where
B. that
水体富营养化的原因是( )
A. 含大量K﹢、Na﹢的废水进入地面水
B. 含大量重金属的废水污染地面水
C. 含大量钙、镁离子的废水进入地面水
D. 含大量氮、磷的废水进入地面水
E. 以上都不是
水体污染的危害不包括( )
A. 急慢性化学性中毒
B. 引起肉毒中毒
C. 引起介水传染病
D. 消化道疾患
E. 致癌致畸致突变
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