题目

The old lady _________when I was in the countryside is said to be still very much alive though in her nineties. A.after whom I looked                                      B.whom I took care C.who I looked after                                         D.of whom I took care 答案：C 解析: 此定语从句的正确说法是whom I took care of/whom I look after。take care of/look after 是固定短语，介词of/after在定语从句中不能提前。 盒中有6个小球，3个白球，记为a1，a2，a3，2，个红球，记为b1，b2，1个黑球，记为c1，除了颜色和编号外，球没有任何区别． (1)求从盒中取一球是红球的概率； (2)从盒中取一球，记下颜色后放回，再取一球，记下颜色，若取白球得1分，取红球得2分，取黑球得3分，求两次取球得分之和为5分的概率．