A.6~7歲 B.6~9歲 C.7~8歲 D.7~9歲 E.8~9歲
A.10s B.30s C.60s D.2min E.5min
A.穿破牙齦時 B.合面露出時 C.對頜牙也已萌出時 D.牙萌出后達(dá)到合平面是 E.無時間限制