In comparison with complex multicellularity, in simple multicellularity: A. there is extensive communication between cells. B. cells are highly differentiated and specialized. C. most cells retain a full range of functions. D. some cells are not in direct contact with the external environment.

The correct option would be C. most cells retain a full range of functions.

Explanation:

In simple multicellularity most cells retain a full range of functions.

Multicellular organisms are organisms that consist of more than one cell, in contrast to unicellular organisms.

All species of living animals, plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium.

"d.) carbon dioxide and hydrogen sulfide"