Kingdom Monera

E. coli is a gram-negative, rod-shaped, motile or nonmotile bacteria. 

• It contains double-stranded DNA. 
• The DNA in E.Coli is not associated with any histone proteins, hence it is known as naked DNA. 
• This DNA has no free ends and is circular.

Therefore, option B) is the correct answer.

Anabaena is a prokaryotic organism. It is a cyanobacteria (blue green algae) which belongs to Kingdom Monera. Like all other prokaryotes, it lacks a true nucleus and other cell organelles.
Therefore, the correct option is (C): Anabaena.

The correct answer is Option 2: Archaebacteria.

Explanation:

Methanogens are a type of archaebacteria (also known as archaea) that produce methane as a by-product of their metabolism. They are typically found in anaerobic environments, such as the intestines of ruminants, swamps, and marshes. Methanogens play a crucial role in the carbon cycle by producing methane (CH4), a potent greenhouse gas.

Eubacteria (Option 1) refers to the "true bacteria" that are different from archaea.

Dinoflagellates (Option 3) are a group of protists, many of which are marine plankton, and are not involved in methane production.

Slime moulds (Option 4) are a group of eukaryotic organisms that exhibit both amoeba-like and fungal-like characteristics, and they do not produce methane.

Thus, methanogens belong to Archaebacteria, which is Option 2.

The digestive system of birds is structured uniquely to help with the breakdown and absorption of food. Unlike many other animals, birds have additional chambers in their digestive system known as the crop and gizzard. The crop serves as a storage pouch, allowing birds to ingest food rapidly and digest it later. The gizzard, a muscular part of the stomach, grinds down food with the help of ingested stones and grit, facilitating digestion.

Among the provided options:

Option 4, which includes Pavo (peacock), Psittacula (parrot), and Corvus (crow), is comprised entirely of birds. These species have a crop and gizzard as part of their digestive systems. In contrast, the other options include animals such as fish, amphibians, and reptiles, which do not have these additional chambers.

Thus, the correct answer is: Pavo, Psittacula, Corvus.