Which are more closely related to complex organisms, bacteria or archaea?

Archaea

Archaeal cells were as simple as bacterium cells. However, research indicates that these simple cells were closer to complex organism known as eukaryotes. This is on the basis of cladistic analysis.Unlike bacteria, archaeal can survive in the harshest of environments.

True

Explanation:

The coelom is the main body cavity found in a group of multi-cellular animals known as metazoans that functions in absorbing shocks, supports immune system, acts as hydrostatic skeleton, and or facilitates a kind of transport system in the animals.

The coelom arise from the mesoderm and as a result, the tissue lining the inner side of the body cavity arises from the same germ layer as the tissue lining the outer side of the body cavity.