题目

在区间[0,4]内随机取两个数a、b，则使得函数f(x)＝x2＋ax＋b2有零点的概率为________． 答案：John may phone tonight,______I'll have to wait at home.                                   [     ]A. in this caseB. in that case   C. in which case                                D. in case