答案肯定是B.
首先分析句子结构.很显然的,句子到nurses为止是主语,其中"____of five men doctors and three women nurses"是定语,修饰前面真正的主语"a medical team"
consist of：主动表被动,由组成相当于be made up of.做定语的时候用doing的形式.
后面因为句子的真正的主语是a medical team,所以谓语动词用单数.
最后整句话整体看一下：
A medical team consisting of five men doctors and three women nurses was sent to the countryside this morning.
意思是：由五个男医生和三个女护士组成的一个医疗团队今天早上被派到了农村地区.