The Appalachian Mountains cover much of which state?

The Appalachian Mountains predominantly cover Pennsylvania, making it the correct choice in this context. This mountain range, which runs along the eastern United States, stretches from Maine in the north down to Georgia in the south, with its foothills extending into Pennsylvania. The state's geography is marked by significant portions of the Allegheny and Pocono Mountains, which are subranges of the Appalachians.

In contrast, while Kentucky and Maryland do host parts of the Appalachian Mountains, they do not encompass as significant a portion of the state's total area as Pennsylvania does. Indiana, on the other hand, is situated further west and does not have any sections of the Appalachian Mountains within its borders, making it an unlikely candidate for a state associated with this mountain range. The prominence of the Appalachians in Pennsylvania is a key factor that solidifies its status as the correct answer.