题目

—Tom came to work last Friday ,but no one has seen him since.        —          he have had an accident ? A．Should             B．Must                   C．Might                D．Could 答案：D全集U=R，若集合A={x|3≤x＜10}，B={x|2＜x≤7}，则（结果用区间表示）（1）求A∩B，A∪B，（CUA）∩（CUB）；（2）若集合C={x|x＞a}，A⊆C，求a的取值范围．