请教这题选哪个?Some of the rubbish ,such as wood ,paper and iron,-a

请教这题选哪个?Some of the rubbish ,such as wood ,paper and iron,＿away over...
请教这题选哪个?Some of the rubbish ,such as wood ,paper and iron,＿away over a long period of time.A.rot B.are rotted C.is rotting D.rots