A:that he needs to think
B:when he has to think
C:therefore he has to work hard
D:then he will need it
如图,△ABC 是等边三角形,点P 是三角形内的任意一点,PD∥AB,PE∥BC,PF∥AC,若△ABC 的周长为36,则PD+PE+PF=( )
①A与____组合,用于____,②B与____组合,用于____,
③B与____组合,用于____,④D与____组合,用于____.
读《社戏》,作者用生动的文字写的主要事情有:
____、____、____、____、____、