A, paramecium body is composed of a cell, belonging to a single-celled organism, and there is no chloroplast in the body, which belongs to heterotrophy.

B Penicillium belongs to fungi. There is no chloroplast in fungal cells, so it can't produce organic matter through photosynthesis, but it can decompose organic matter, which belongs to heterotrophy.

C. Pteridium aquilinum, with the differentiation of roots and leaves, is higher than algae plants, with chloroplasts in cells, which can make organic matter through photosynthesis and belong to autotrophic type. C is correct.

D. Rhizobium belongs to bacteria, and there is no chloroplast in bacteria, which belongs to heterotrophy. D error.

So choose: C.