Concept:Brooding diseases mainly affect young chicks during the first few weeks of life.
Explanation:Yolk sac infection is common in young chicks during brooding and can cause high mortality.
Coccidiosis frequently occurs in chicks, especially when brooding conditions are warm and damp.
Pullorum disease is a bacterial infection that typically affects chicks during the brooding period.
Fowlpox is a viral disease that generally appears in older birds, not in chicks during brooding.
Therefore, the diseases commonly found during brooding are I, II, and IV only.
Answer:Option B (I, II and IV only)