历史学家认为，我国原始社会的氏族聚落居民已大量种植水稻，我国

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问题

历史学家认为，我国原始社会的氏族聚落居民已大量种植水稻，我国是世界上最早种植水稻的国家之一。下列遗址能够证明这一论点的是（）

A．元谋人遗址

B．北京人遗址

C．半坡遗址

D．河姆渡遗址

答案

题目分析：中国很早就出现了原始的农耕，是世界上最早种水稻的国家，距今约七千年的河姆渡原始居民的生活，生动地展现了长江流域原始农耕的图景。河姆渡原始居民已使用磨制石器，用耒耜耕地，种植水稻。

选择题

（1）铜粉放入稀H₂SO₄中，加热后无明显现象，当加入KNO₃ 后，铜粉质量减小，溶液变蓝，同时气体逸出，该反应的离子方程式为。（2）在含Cu^＋的酶的活化中心内，亚硝酸根离子(NO₂^-)可转化为NO，写出Cu^＋与亚硝酸根离子在酸性水溶液中反应的离子方程式。

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单项选择题

It’s all annual back-to-school routine. One morning you wave goodbye, and that (1) evening you’re burning the late-night oil in sympathy. In the race to improve educational standards, (2) are throwing the books at kids. (3) elementary school students are complaining of homework (4) What’s a well-meaning parent to do.As hard as (5) may he, sit back and chill, experts advise. Though you’ve got to get them to do it, (6) helping too much, or even examining (7) too carefully, you may keep them (8) doing it by themselves. "I wouldn’t advise a parent to check every (9) assignment," says psychologist John Rosemond, author of Ending the Tough Homework. "There’s a (10) of appreciation for trial and error. Let your children (11) the grade they deserve. " Many experts believe parents should gently look over the work of younger children and ask them to rethink their (12) . But "you don’t want them to feel it has to be (13) ," she says.

That’s not to say parents should (14) homework-first, they should monitor how much homework their kids (15) . Thirty minutes a day in the early elementary years and an hour in (16) four, five, and six is standard, says Rosemond. For junior-high students it should be " (17) more than an hour and a half," and two for high school students. If your child (18) has more homework than this, you may want to check (19) other parents and then talk to the teacher about (20) assignments.

13（）

A.perfect

B.better

C.unusual

D.complete

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