uniform前为什么要加a

uniform前为什么要加a uniform前+a还是an The policemen are in uniform为什么uniform不加s uniform 前加的是a还是an ,哪umbrella 呢 His brother always wears---uniform to school.A.a B.anC./D.the 正确答案是C uniform可数吗?什么情况下 uniform前面加冠词?“穿制服”是wear uniform 还是wear a uniform?为什么这道题不能加冠词呢? wear a uniform为什么不用an we wear school uniform at school.uniform为什么不加s? uniform前面加的是an还是a? I am worker 为什么要在worker前加a? world前为什么加冠词a uniform为什么是a uniform而不是an uniform? uniform为什么是a uniform而不是an uniform? a uniform还是an uniform急 wear a uniform 还是wear uniform 请问 a uniform gravitational field 中的 uniform a还是an uniform meke a uniform是什么意思 英语为什么名词前有时加the有时加a