Find the correct statement

To determine the correct statement, let us analyze each option step-by-step:

1. Paramecium, Penicillium and Plasmodium belong to the same kingdom:
- Paramecium and Plasmodium are unicellular eukaryotes and belong to the kingdom Protista.
- Penicillium is a multicellular eukaryotic mold and belongs to the kingdom Fungi.
- Since they belong to different kingdoms, this statement is incorrect.

2. lichen is a symbiotic association of an alga and Protozoan:
- A lichen is a symbiotic, mutually beneficial association between an alga (or cyanobacterium) and a fungus.
- There is no protozoan partner involved in this association. Thus, this statement is incorrect.

3. Nostoc and Anabaena come under Protista:
- Nostoc and Anabaena are filamentous cyanobacteria (blue-green algae).
- Since they are prokaryotic organisms, they are classified under the kingdom Monera, not Protista. Therefore, this statement is incorrect.

4. Yeast is a fungus and is used in bread and beer production:
- Yeast is a unicellular, eukaryotic organism belonging to the kingdom Fungi.
- It is widely used in commercial baking and brewing because it ferments sugars to produce ethanol and carbon dioxide (${\mathrm{CO}}_2$), which helps bread rise and provides alcohol in beer. This statement is scientifically accurate and correct.