a eraser（橡皮）还是an eraser?为什么?

a eraser（橡皮）还是an eraser?为什么? 一块橡皮翻译是a eraser还是an eraser 橡皮的单数是a eraser还是an eraser an eraser 还是 a eraser eraser前加a还是an? black eraser前加an 还是a eraser前面是加a还是an 英语面临一个翻译时比如翻译：一块橡皮 an eraser 一本书 a book 怎么识别加a还是加an呢? She n_ a pencil and an eraser. eraser是橡皮,怎么读 This is eraser,eraser is inThis is eraser,eraser is in the pencil box.A.a;The B.an;The C.an;An D.the;The(对了,) End.Of.An.Era It`s an eraser.为什么加an不加a I have a ruler ahd an eraser.(改为否定句） I find （ ）eraser in the classroom.括号里可填a/an/the. Whose ____ eraser is this?(a 或an或the或／）应选哪个 Is that an eraser?( ),it's a dictionary此处填NO还是NO IT ISN’T? It's an eraser.中文怎么翻译? E-R-A-S-E-R,eraser.怎么翻译?