Mr. Williams owns a stable in the countryside. He created the expression below to represent the number of horses at the stable t years after he began boarding horses.

Which statement below best describes the coefficient, 30?
A.
the rate at which the number of horses was changing before Mr. Williams began bording horses
B.
the rate at which the number of horses boarded changes
C.
the increase in the number of horses borded each year
D.
the initial number of horses boarded