【初三英语】分数+of+n.作主语时动词用单数还是复数? 1.——How many teachers are there

【初三英语】分数+of+n.作主语时动词用单数还是复数? 1.——How many teachers are there in your school?
——About 200. One third of them ____ men teachers.
2.A third of the population of the city ____ their own cars.
A.has B.have C.had D.is
为什么第一题答案给的是is,第二题给的是B呢?我觉得第二题应该选A呢……
请详细解答,谢谢~