What is a sign of actively growing ringworm on the hand?

Active ringworm, which is a common fungal infection, typically presents as circular red lesions on the skin. These lesions are characterized by raised edges and a clearer center, resembling a ring, hence the name "ringworm." The presence of these circular red lesions indicates that the fungus is actively growing and spreading on the skin.

The other choices do not accurately describe the manifestations of ringworm. Worms on the skin would suggest a different type of infection entirely and is not associated with ringworm, which is a fungal infection rather than a parasitic one. Leaking of pus can indicate a secondary bacterial infection or other skin condition but is not a typical feature of ringworm. Boils are also unrelated to ringworm and refer to deeper infections of the hair follicle. Therefore, the visible circular red lesions are the primary sign that indicates the presence and active growth of ringworm on the hand, making it the correct choice.