I believe the answer is C) reproductive isolation.
Hope this helps!
A vaccine is a medical material that mimics the pathogen, but in a harmless way. When our body's immune fights it off, it remembers how to fight the real pathogen when it enters our body. So, it protects us from diseases.
Protozoans are free-living or parasitic eukaryotic organisms. They feed on dead and decay matter.
<h3>What are protozoans?</h3>
Protozoans are microorganisms. They are eukaryotic organisms, and they can be parasitic or free-living. They feed on dead and decay matter. Examples are amoeba, euglena, paramecium, etc.
Organisms that eat dead or decay matter are called decomposers. They clean the environment by eating the debris or decay, matter. Microorganisms like bacteria or protozoans are decomposers.
Thus, protozoans are decomposers as they feed on dead and decay matter.
To learn more about protozoans, refer to the link:
brainly.com/question/12726711
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The answer to your question is going to be is B
