The study of microorganisms is termed as

The correct answer is Microbiology.

Microbiology is the branch of science that deals with the study of microorganisms. Microorganisms are very, very small living things that you can't see with your bare eyes, like bacteria, viruses, fungi, and protozoa. You need a microscope to see them! Microbiologists study how these tiny creatures live, where they live, what they do, and how they affect us (both good and bad).

Now let's quickly look at why the other options are not correct:

Option A: Evolution is the study of how different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the Earth. It's about changes over a very long time, not specifically about microorganisms.

Option C: Zoology is the scientific study of animals. This includes everything from insects to elephants, but not the tiny, microscopic organisms.

Option D: Palaeontology is the scientific study of life that existed in prehistoric times through the examination of fossils. It focuses on ancient life forms, usually much larger than microorganisms, and is based on their preserved remains (fossils).

So, when you hear 'microorganisms', think 'Microbiology'!