Which of the following bonds can be treated as weak bonds or secondary bonds（）
A. dipole–dipole interactions
B. the London dispersion force
C. hydrogen bonding
D. metallic bonding
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What are the characteristics of the same main group in the periodic table（）
A. The outermost layers have the same number of electron
B. They have the similar chemical properties
C. The number of electron layers from top to bottom gradually increases
D. The atomic radius from top to bottom gradually increases
Specific amount of water should be used to prepare normal consistency of cement paste, otherwise cement properties would be influenced. Which choice in the following is the corresponding property be a
A. The values of compressive and flexural strength
B. Comparability of setting time and volume soundness
C. Release amount of hydration heat
Determination of strength grade
Ordinary Portland cement is not suitable for（）
A. cold region
B. wet environment
C. mass concrete
D. high loading condition
Too much free-CaO or free-MgO in cement would lead to（）
A. inappropriate setting time
B. poor soundness
C. failure to meet strength requirement
D. undesirable workability
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