问题
选择题
When he was asked about the question where he was last night, he was ______. [ ]
A. at loss
B. in a loss
C. at a loss
D. with losses
答案
答案：C
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When he was asked about the question where he was last night, he was ______. [ ]
A. at loss
B. in a loss
C. at a loss
D. with losses
答案：C
h，求该磁场磁感应强度B的大小。