第2个回答 2011-11-10
Using a or an depends on the sound that begins the next word. So...
- a + singular noun beginning with a consonant: a boy; a car; a bike; a zoo; a dog
- an + singular noun beginning with a vowel: an elephant; an egg; an apple; an idiot; an orphan
- a + singular noun beginning with a consonant sound: a user (sounds like 'yoo-zer,' i.e. begins with a consonant 'y' sound, so 'a' is used); a university; a unicycle