3、表示正在发生的动作或发生的事情。(3)The sun isshining.(1)Thebirdsaresinging.(2)Theducksareswimming.Itisdringkingcola.Whatisitdoing?Theyaresinging.Theyarehavingapicnic.Heisswimming.用下列词的正确形式填空。Iam_________(swim)now.He_____(be)doinghomeworknow.Weare_______(lookat)somed