题目

 The old couple has a son and two daughters, _______ are college students now.      A. all of whom       B. all of them         C. both of whom   D. both of them 答案：A（8分）某温度（t℃）时，水的Kw＝10-13mol2·L-2，则该温度（填大于、小于或等于）　　　25℃。将此温度下pH=11的NaOH溶液aL与pH=1的H2SO4的溶液bL混合，则：（1）若所得混合液为中性，则a∶b                  ；（2）若所得混合液的pH＝2，则a∶b                ；