The correct answer is d) fungi.
Fungi are a diverse group of microorganisms that possess complex internal structures known as cell compartments. Unlike bacteria and archaea, which are prokaryotic and lack these internal compartments, fungi are eukaryotic, meaning they have a well-defined nucleus and organelles within their cells. This cellular complexity allows them to perform various metabolic processes efficiently.
In addition to their structural characteristics, many fungi play a crucial role in the ecosystem as decomposers. They break down organic matter, recycling nutrients back into the environment. This decomposition process is vital for soil health and helps support plant growth, making fungi integral to ecological balance.