Task: Question Generation
Input (English): Background Paragraph: The epidermis also contains melanocytes , which are cells that produce melanin. Melanin is the brownish pigment that gives skin much of its color. Everyone has about the same number of melanocytes, but the melanocytes of people with darker skin produce more melanin. The amount of melanin produced is determined by heredity and exposure to UV light, which increases melanin output. Exposure to UV light also stimulates the skin to produce vitamin D . Because melanin blocks UV light from penetrating the skin, people with darker skin may be at greater risk of vitamin D deficiency. 
Story: Matt and his brother Jesse are twins. They look almost identical. If it weren't for the fact that Jesse has a slightly darker skin complexion you wouldn't be able to tell them apart. In fact one year Matt was out in the sun for a long time and picked up a bit of a tan so they actually did look exactly alike.
Output (English): Which was responsible for Matt's complexion being as dark as Jesse's, UV light or heredity?