___________ hour (a)an (B) a

___________ hour (a)an (B) a They will be back ___________ A.for an hour B.after an hour they walked for.A,an hour B.half a hour C,half an hour 选哪个 a hour 还是 an hour? a hour 还是 an hour ____ hour (A) a (B) an 并说明理由 half an hour or a half hour? a half hour还是half an hour? a one -hour还是an one-hour they will go back () A after half an hour B in half an hour I’m going to the shop _____.A.for an hour B.after an hour C. ( )The train will arrive_______.A.after an hour B.in an hour