B, the formation of enzymes secreted outside the cell goes through several stages, such as ribosome synthesis, endoplasmic reticulum and Golgi body processing, but the enzyme of the cell itself is unnecessary, and B is wrong;

C. Existing autotrophs (such as cyanobacteria and nitrifying bacteria). ) and heterotrophic bacteria (saprophytic bacteria, etc. ) In prokaryotes. C is correct;

D, SARS virus has no cell structure, so there is no cytoplasm, D error.

So choose: C.