organisms whose cells do not contain a well-defined nucleus are
placed in the kingdom fungi.
a. true
b. false

Organisms whose cells do not contain a well-defined nucleus are  placed in the kingdom Fungi is false.

False.

Explanation:

Fungi are eukaryotes that contain many membrane-bound organelles and a nucleus. The Fungi kingdom consists of many living organisms though fungi are more plant-like organisms but are closely related to animals.

Fungi are generally heterotrophic because they use the organic compound for a source of energy.

Many fungi produce haploid cells that undergo mitosis to become multicellular. They play an important role in the ecosystem because they break down organic plus inorganic materials into molecules.