Final answer:
Option C is the correct answer. Doctors check for swollen lymph nodes to detect an immune response, often caused by infections, inflammation, or cancer. They filter lymph and are part of the immune system. Persistent swelling may also indicate more serious conditions like lymphoma.
Step-by-step explanation:
Doctors check for swollen lymph nodes because these are often signs of an immune response. Lymph nodes are small, bean-shaped organs that are part of the lymphatic system, which plays a crucial role in fighting infections. They filter lymph, a fluid that contains white blood cells, and swell in response to the presence of infections, inflammation, or cancer.
Concerning the options provided, C. Swollen lymph nodes may indicate an immune response is accurate because they typically enlarge as part of the body's defense against pathogens or when they are fighting an infection, whether viral or bacterial. While option D suggests that bacteria and viruses can affect the lymph nodes, which is true, the presence of pathogens is not the only reason for enlargement.
For a patient like Wei, persistent swollen lymph nodes without improvement after antibiotics might also indicate other underlying conditions, including lymphoma, which is a form of cancer. A biopsy of the lymph node may be necessary to confirm such a diagnosis, as was the case with Wei.