we walked 什么 an hour

we walked 什么 an hour we walked () an hour 填介词 they walked for.A,an hour B.half a hour C,half an hour 选哪个 We have an hour for lunch等于什么 We talked___half an hour ago We covered ___ an hour that day. We are leaving in an hour we ,exercising ,spend,an ,usually ,hour ,hair , Half an hour =什么? half an hour? 什么意思? an hour ago和an hour later有什么区别? in an hour /within an hour用什么时态