John is driving around town. When he reaches the gas station, he notes that he has traveled 12 miles. He reaches home 2 hours later and notes that he has traveled 31 miles. If d represents the distance and t represents the time, in hours, John has traveled since the gas station, which of the following equations can be used to model this situation?
A. d = 9.5t - 12

B. d = 19 + 12t

C. d = 12t + 43

D. d = 9.5t + 12