usa加a还是an是a usa 还是an usa

usa加a还是ana usa还是an usa usa加a还是an是a usa 还是an usa 是a USA Stamp 还是an USA Stamp（一张美国邮票）,正确呢? 是in the USA,还是in USA? eraser前面是加a还是an advice前面是加a还是an 是a还是an 英语翻译是 tips for going on an educational exchange to the USA还是 tips for going to the USA for educational exchange还是 tips for educational exchange in the USA哪个好,有没错 关于USA的用法在句子里出现的USA 前面一定要加the吗?The USA 还是 USA? orange前加an还是加a “answer”前面是加“a”还是加“an”? aunt的单数是加a还是加an. actor的单数是加a还是加an. taxi前面是加a还是加an? actress的单数是加a还是加an. banana的单数是加a还是加an? A前面加an 还是a 快 A is rarely seen in the USA.中,rarely是修饰is还是seen