7. Which of the following types of pathogen is responsible for the common cold?
Answer: B
Virus
The pathogen responsible for the common cold is a virus. Specifically, rhinoviruses are the most common viral agents that cause this illness.
A) Bacterium
Bacteria are single-celled microorganisms that can cause infections, but they are not responsible for the common cold. In fact, the common cold is primarily caused by viral infections, making this option incorrect.
B) Virus
Viruses are the correct type of pathogen for the common cold. They invade host cells and replicate, leading to the symptoms associated with colds. Rhinoviruses are the most frequent culprits, confirming that this choice is accurate.
C) Fungus
Fungi are a diverse group of organisms that can cause various infections, particularly in immunocompromised individuals, but they do not cause the common cold. This option is therefore incorrect.
D) Protozoan
Protozoans are single-celled organisms that can lead to diseases such as malaria and giardiasis, but they are not linked to the common cold. Thus, this option is also incorrect.
Conclusion
The correct answer is "virus" because it directly identifies the type of pathogen that causes the common cold, specifically through the action of rhinoviruses. All other options—bacterium, fungus, and protozoan—are not involved in the etiology of the common cold, making them incorrect choices.