I thing this documentrary is boring 这样变复数句大神们帮帮忙

I think this story is boring变复数句~没立你为正确答案~ this.is pen变复数句 I think this programme is boring的同义句 that documentary is boring{改为复数句 He has a baseball改为复数 This story is boring改为反义句 Is this a pen?（变复数句） this is knife in the box（变复数句 this is a box.变复数句___________? This is a pen变为复数句,怎么变 This is a horse.变该句为复数形式 This set of rulers is blue 变复数句 This baby is sleeping on the train变复数句