The Great Plains east of the Rocky Mountains have a(n) arid climate.
оа
Oь
humid continental climate.
C
temperate marine climate.
Od
semiarid climate.

i think the answer is a.keratin is the pigment responsible for skin color.

look at this it will give you up to 17 answers  

answer; the code in musculoskeletal system subsection is associated with deep tissue possibly to the bone;