Answer:
Option A. 
Step-by-step explanation:
Let
d -----> the number of days
C(d) -----> the total cost
we know that
The linear equation in slope intercept form is

where
m is the rate or slope of the linear function
b is the y-coordinate of the y-intercept
In this problem we have that

The slope of the linear equation is equal to the charge of $25 per day to board dogs
so

The y-intercept is the value of y when the value of x is equal to zero
In this problem the C-intercept is the total cost when the number of days (d) is equal to zero
The C-intercept is equal to the cost of the bath $12
so

substitute the values
