A scientific study found that the relationship between the remaining lifespan in days of a rat with a certain disease and the number of doses given to the rat of a new experimental drug meant to treat the disease can be approximated by the equation y = 2x + 30, where x is the number of doses and y is the remaining lifespan. What does 30 represent in the equation?
A
the remaining number of days the rat can be expected to live if it isn't given any doses of the new experimental drug

B
the remaining number of days the rat can be expected live if it is given 28 doses of the new experimental drug

C
the number of doses of the new experimental drug that the rat must be given for its remaining life expectancy to increase by 2 days

D
the number of doses of the new experimental drug that the rat must be given for its remaining life expectancy to increase by 28 days