Pls help my question in photo

Allusion and illusion. an allusion is an indirect reference, whereas an illusion is something that is unreal or incorrect. each of the nouns has a related verb form: allude “to refer indirectly to,” and illude (not a very common word), which may mean “to delude or deceive” or “to subject to an illusion.”

To form soil, the two processes which must occur are erosion and weathering, so the correct answer is "soil formation is a continuous presses, but also one which takes a long time, it can sometimes take more than five hundred years for 1cm of soil to form.