The correct option is D Hydra
The ageing is very slow or is not seen with the human eye in unicellular organisms but they do age. They undergo constant spontaneous DNA damage that can lead to the death of cells when it no longer able to reproduce. Plants and parrot are multicellular organisms with the higher level of complexity. The complexity is such that cell divisions are limited and when the cell is not able to divide, it ages with the decay of organelles and finally dies. So these organisms do age and die after a perticular period of time. but Hydra is the only species that does not age and lose its capability to reproduce. So we can say that ageing is slow or absent in hydra.