Generally speaking, the number and proportion of various organisms in the ecosystem are relatively stable. This shows that the ecosystem has certain self-regulation ability. The adjustment ability of ecosystem depends on its own structural characteristics, but the resources and space of ecosystem are limited, so its self-adjustment ability is limited. Generally speaking, the more kinds of organisms in the ecosystem, the more complex the nutritional structure, and the greater the self-regulation ability. On the contrary, the self-regulation ability is small.

So choose: B.