Question

Which organisms contain the smallest, least complex cell types? animal cells bacteria cells plant cells fungal cells?

Answer 1

bacteria cells are small and simple

Answer 2

Answer: bacteria cells
Bacterial cells are smaller and simpler than any other of the options.
Bacterial cells don't contain chloroplasts(unlike plant cells), bacterial cells lack a nucleus (they have the genetic information spread in the cytoplasm) and lack a mitochondria.