Analysis of test questions: photosynthetic bacteria, nitrifying bacteria, etc. It can convert inorganic matter into organic matter, which belongs to producers, so it is wrong; All autotrophs are producers, so ② is correct; Plants are not necessarily producers, for example, dodder is a consumer, so it is wrong; Earthworms, dung beetles and so on. They are all decomposers, so they are wrong; Heterotrophs can be a consumer or a decomposer, so ⑤ is wrong. To sum up, A is correct.

Test center: This topic examines the structure of the ecosystem, aiming at examining the examinee's ability to understand the main points of the content and grasp the internal relationship between knowledge.