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【单选题】
如图所示,电流 I 由长直导线 1 经 a 点流入由电阻均匀的导线构成的正方形线框,由 b 点流出,导线 2 返回电源 ( 导线 1 、 2 的延长线均通过 O 点 ) .设载流导线 1 、 2 和正方形线框中的电流在框中心 O 点产生的磁感强度分别用 、 、 表示,则 O 点的磁感强度大小A.
B ≠ 0 ，因为虽然 B 3 = 0 ，但
B.
B = 0 ，因为 B 1 = B 2 = B 3 = 0
C.
B ≠ 0 ，因为虽然 ，但 B 3 ≠ 0
D.
B = 0 ，因为虽然 B 1 ≠ 0 、 B 2 ≠ 0 、 B 3 ≠ 0 ，但
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举一反三
【简答题】In this article the author relies chiefly on ______to support his main arguments.
【单选题】The author begins his article with ______.
A.
an anecdote about his grandparents
B.
a quotation from his grandparents
C.
a description of, and a comment on, his grandparents' principle of life
D.
his admiration at his grandparents' way of life
【单选题】His article concerning population control was published in the ( ) issue of China Daily.
A.
latest
B.
lately
C.
late
D.
later
【简答题】In this article the author uses ______ to support many of his important points in the news story.
【单选题】The author begins his article with ______________________.
A.
an anecdote about his grandparents
B.
a quotation from his grandparents
C.
a description of, and a comment on, his grandparents' principle of life
D.
his admiration of his grandparents' way of life.
【单选题】The author begins his article with _____.
A.
a specific example from his own experience
B.
a specific example based on a story he heard
C.
a summary of his main argument
【简答题】In this article, the author relies chiefly on ______ to support his main ideas.
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