Which of the following best describes the cause of infection and a key structure involved in fighting infection in humans?

• A. Viruses are the only cause of infection, and red blood cells fight infections.
• B. Bacteria are common causes of infection, and white blood cells help fight infections.
• C. Fungi cause all infections, and platelets are the main defense against infection.
• D. Protozoa are the primary cause of infection, and antibodies are not involved in fighting infection.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the different types of infectious agents mentioned: viruses, bacteria, fungi, and protozoa. Each of these can cause infections, but their prevalence and roles differ.
2. Step 2: Recognize the key components of the human immune system involved in fighting infections. These include white blood cells (leukocytes), antibodies, red blood cells, and platelets, each with distinct functions.
3. Step 3: Recall that white blood cells are the primary cells responsible for identifying and destroying pathogens such as bacteria, viruses, fungi, and protozoa. They play a central role in the immune response.
4. Step 4: Note that red blood cells mainly transport oxygen and do not participate in fighting infections, while platelets are involved in blood clotting, not immune defense.
5. Step 5: Understand that antibodies are proteins produced by certain white blood cells to specifically target pathogens, so they are indeed involved in fighting infections.