According to Bacon, facts______.
A. are determined by observations
B. can only be understood through logical reasoning
C. have a hierarchy
D. are gathered by illiterate assistants
橡胶材料除了具有一般非金属材料所共有导热性差、强度低等特点外，还有（ ）极大的特点。
A. 弹性
B. 塑性
C. 韧性
D. 刚性
车床夹具的（ ）要跟支承件对应，这是防止工件装夹变形的保证。
A. 夹紧力
B. 轴向力
C. 辅助支承
D. 周向力
The symbols are said to be arbitrary because they do not ______what they represent.
A. resemble
B. mean
C. differ from
D. change
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