a half hour对吗

half an hour or a half hour? a half hour还是half an hour? half a hour a half of an hour two hours and half a hour 2个半小时 这种表达对吗 half an hour 和a half hour有什么区别? an hour and half还是an hour and a half a half hour later\after half an hour\after half an hour late half an hour,half hour,a half hour哪些对,那些错 they walked for.A,an hour B.half a hour C,half an hour 选哪个 He was here().A.half an hour before B.half hour ago C.half a a half hour还是a haif hours