A formal region defines an area in which A
a core dominates its surrounding hinterland
B
a transportation network links different types of land use
С
there is uniformity in one or more physical or human characteristics
D
there are significant geographic variations in physical or human characteristics
E
a unified government system has been established

The peak above is part of the  sierra madre occidentals ,  a chain of volcanic mountains that runs through the middle of central america. 

How is this even a question?

Your answer is d. silli hope this ! : ) i left an explanation down below if you need it: a sill forms when hot magma squeezes between layers of rock to form a hardened sheet of rock. a sill is basically a tabular sheet intrusion between old layers of sedimentary rock, volcanic beds, or in the direction of foliation inherent in metamorphic rock. the word sill means a concordant intrusive sheet.