unusual前面用a还是an,alien前面用a还是an

unusual前面用a还是an,alien前面用a还是an AMAZING UNUSUAL的前面是A还是AN most an unusual 还是 a most unusual 是a unusual还是an unusual 是a unusual还是an ununusal? 单词“unusual”前应填a,还是an usually unusual前面加 分别加什么( a an) 字母A前面用a还是an 是a upset boy 还是 an upset boy还有是a unusual lady还是an unusual lady? s前面用a还是用an university前面用“a”还是用“an”? year前面用a 还是用an exciting前面介词用a 还是an mp4前面用an 还是a egg前面用a,还是an? exciting前面用定冠词a还是an engineer 前面用A 还是AN 字母“n”前面用a还是an?