水蚀因流失程度及其发展形态不同，可分为那两类？

原文：W: Whtre you doing here M: I’m prepring my fishing tools. W: Wht for M: I’m going to fish with some of my friends. W:re you fond of fishing M: Yes. I like fishingfter schoolnd on Sundys. W: When did you get such hobby M: Longgo. You know, my fther is fond ofnd very goodt fishing. When I ws child, he took me to the riverside to see him fishing. I found fishing very interesting then. Well, wht’s your hobby W: I’m very interested in mking home movies. But I hven’t got movie cmer. M: Ilso like tking photosnd I hve Jpnese-mde cmer. W: I tke lot of photos, too. But I’m more interested in the history of film, so I relly enjoy using film cmer. I’ll buy one of my own somedy. Wht is the mn doing now He is fishing. B．He is prepring for fishing. C．He is tking photos.A．He is fishing．B．He is preparing for fishing．C．He is taking photos．