According to the geometrical shape, crystal lattice imperfections are classified . 根据几何形状，晶格缺陷分为哪些类型（）
A. Point Defects
B. Line Defects
C. Planar Defects
D. none of them
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In practical production, when metals are cooling, .在实际生产中，当金属冷却时，下列说法正确的是（）
A. actual crystallizing temperature（实际结晶温度） is always below theoretic crystallizing temperature（理论结晶温度）
B. actual crystallizing temperature is always equal to theoretic crystallizing temperature
C. actual crystallizing temperature is always higher than theoretic crystallizing temperature
D. actual crystallizing temperature and theoretic crystallizing temperature have no relationship
Which of the following are the properties of crystals（）
A. long-range order
B. have fixed melting points
C. anisotropic各向异性
D. short-range order
E. isotropic各向同性
Which of the following are the methods of getting fine grains（）
A. Increase the degree of supercooling
B. Inoculation
C. Vibration and stirring
D. Reduce the degree of supercooling
Dislocation（位错） is belonging to（）
A. Body Defects
B. Planar Defects
C. Line Defects
D. Point Defects
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