Final answer:
Africa is the second-largest continent after Asia, hosts the majority of HIV-positive cases, and West Africa was the region most involved in the Trans-Atlantic slave trade.
Step-by-step explanation:
The student's question is asking which continent is the largest after Asia. According to geographic facts, Africa is the second-largest continent following Asia. Therefore, the answer to the question is 'a) Asia'. Africa is also the continent with the highest number of HIV-positive cases, and the region most directly involved in the Trans-Atlantic slave trade was West Africa.