Final answer:
The shared traits between archaeans and bacteria are the lack of a nuclear envelope and the presence of a circular chromosome, not the composition of their cell walls or plasma membranes.
Step-by-step explanation:
Archaeans and bacteria, both being types of prokaryotic cells, share several traits despite their distinct domains. The correct answer to the question is c) lack of a nuclear envelope and presence of circular chromosome. Both archaea and bacteria lack a nuclear envelope, which means their genetic material is not enclosed within a membrane-bound nucleus. Additionally, they both typically have their genetic material organized in a circular chromosome. One of the main differences between these domains is the composition of their cell walls; archaeal cell walls do not contain peptidoglycan while bacterial cell walls do. Moreover, the plasma membrane composition also differs, with bacteria having plasma membranes made up of fatty acids, while archaea have membranes composed of phytanyl groups.