不计阻尼，不计自重，不考虑杆件的轴向变形，下图所示体系的自振频率为()
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(汉译英)你们班里有多少同学的父母在政府机关工作？
The most recent figures show that the area of rainforest _______(destroy) last year alone was bigger than the size of Great Britain and Ireland.
________ (tell) us what to do , he left.
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