Introduction:
Puccinia is a genus of plant-pathogenic fungi that belongs to the kingdom Fungi. It is a well-known group of rust fungi that infect various plants and cause significant damage to crops. In this response, we will discuss the kingdom to which Puccinia belongs and provide a brief explanation of the other options given in the question.

Kingdom Fungi:
- Puccinia belongs to the kingdom Fungi. Fungi are eukaryotic organisms that include a wide range of organisms such as mushrooms, yeasts, molds, and rusts. They are heterotrophic, meaning they obtain nutrients by absorbing organic matter from their surroundings.
- Fungi are characterized by having cell walls made of chitin, a unique polysaccharide, and they reproduce by producing spores. They play essential roles in ecosystems as decomposers, pathogens, and symbionts.

Options:
1. Whet, Fungi:
- "Whet" is not a recognized term in biology. It seems to be a typographical error or a misinterpretation.
- However, if we assume it is meant to be "wheat," then it should be noted that wheat belongs to the kingdom Plantae, not Fungi. Wheat is a cereal grain that is widely cultivated for its edible seeds.

2. Euglena, Fungi:
- Euglena is a unicellular organism that belongs to the kingdom Protista, specifically the phylum Euglenozoa.
- Euglena is a photosynthetic organism that contains chloroplasts and can produce its own food through photosynthesis. It possesses characteristics of both plants and animals.

3. Nostoc, Monera:
- Nostoc is a genus of cyanobacteria, commonly known as blue-green algae.
- Cyanobacteria are prokaryotic organisms that belong to the kingdom Bacteria, specifically the phylum Cyanobacteria. Therefore, they are classified under the kingdom Monera.
- They are photosynthetic bacteria that can fix atmospheric nitrogen and form colonies or filaments.

4. Mycoplasma, Monera:
- Mycoplasma is a genus of bacteria that lack a cell wall.
- It belongs to the kingdom Bacteria, specifically the phylum Tenericutes. Mycoplasmas are classified under the kingdom Monera.
- They are parasitic or commensal organisms that can infect animals and plants, causing diseases.

Conclusion:
Puccinia belongs to the kingdom Fungi. The other options given in the question are incorrect. Wheat belongs to the kingdom Plantae, Euglena belongs to the kingdom Protista, Nostoc belongs to the kingdom Monera (specifically Cyanobacteria), and Mycoplasma belongs to the kingdom Monera (specifically Tenericutes).