弯曲应力有正应力和剪应力之分。一般正应力由弯矩引起,剪应力由剪力引起。( )
A. 对
B. 错
梁在纯弯曲时,中性轴的正应力为零。( )
A. 对
B. 错
________ is considered the greatest masterpiece of Chinese calligraphy in history.
Along the River During the Qingming Festival
B. The Preface to the Lanting Collection of Calligraphy
C. Galloping Horse
D. The Foolish Man Moving Mountains
Calligraphy retains the beauty of ________ and illuminates the spiritual beauty of human beings.
A. sky
B. earth
C. world
D. nature
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