Final answer:
Erythema chronicum migrans (ECM) is both a red bull's-eye rash and a spirochete-infected skin lesion that signifies the presence of Lyme disease following a tick bite.
Step-by-step explanation:
Erythema chronicum migrans (ECM) is the characteristic red bull's-eye rash that appears at the site of a tick bite and is often associated with Lyme disease. This rash, also referred to as erythema migrans, develops 3 to 30 days following the bite of a tick carrying the Borrelia burgdorferi bacterium. The rash is usually warm to the touch, and its presence is a diagnostic indicator of Lyme disease. ECM can also be considered as a spirochete-infected skin lesion due to the nature of the bacteria causing it.
Therefore, the correct answer to the question 'Erythema chronicum migrans (ECM) is the ________ caused by tick bite?' is Both B and C: B. red bull's-eye rash, and C. spirochete-infected skin lesion.