题目

下列物质中，只含有离子键，不含有共价键的是（   ） A. Na2O2    B. KOH    C. CaCl2    D. CO2 答案：【答案】C 【解析】A 既含有离子键，又含有共价键。 B KOH既含有离子键，又含有共价键 C CaCl2只含有离子键 D CO2只含有共价键 --- Have we ______ water?--- Yes, _____. We’d better get some.A．run out of; we have run it outB．run out of; our water has run outC．run out of; our water has been run outD．run out; our water has been run out.