Every year, many people get sick from the common cold. While there are medicines that can help with the symptoms, there is nothing that can cure or prevent a cold. What kind of pathogen causes the common cold? A. Bacterium
B. Fungus
C. Parasite
D. Virus

D. Virus

Explanation:

based on this website: https://www.hopkinsmedicine.org/health/conditions-and-diseases/common-cold#:~:text=What%20causes%20the%20common%20cold,the%20rhinoviruses%20causes%20most%20colds.

Common colds are caused by various kinds of viruses. Rhinoviruses cause most colds.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.

the answer is :