if 可以省略they are吗,就像while（they are）good这样?

if 可以省略they are吗,就像while（they are）good这样? They are （my） good friends.就划线部分提问 they are good friends while they are old enough They learn () while they are watching and (） They are from the United States.我可以写成这样吗?They are from the U they are not good （ ）your study. what good children they are they are good frends意思 They are good at______(run). they are heving a good 这句话对么?they would work better if they are in a good mood.