an houe ago中HOUR不是元音字母开头 为什么用AN?

an houe ago中HOUR不是元音字母开头 为什么用AN? an hour ago和an hour later有什么区别? There are 60 minutes in an (hour)为什么an 后面填 hourhour的H不是元音字母 She has swum since half an hour ago.不是说ago不能用在完成时吗? tom ____(play)football an hour ago an hour ago 算不算段时间 since 还是 for an hour ago They left an hour ago变成现在完成时 half an hour ago 什么意思? Jim finished ( ) his homework an hour ago It started to rain an hour ago Miss Gao left an hour ago 同义句转换 Miss Gao an hour ago Miss Gao left an hour ago的同义句 Miss Gao _____ an _____ hour ago. Sorry,I ordered my food half an hour ago.对“half an hour ago”提问 He was here().A.half an hour before B.half hour ago C.half an hour ago lucy went out an hour ago.she will be back in half an hour. She got up an hour ago.换成She ( ) ( ) ( ) for an hour. We cooked the dumplings an hour ago.(用for an hour改写）