21-04SD 数学2 Q27

x 代表distance, y代表cost (in billions of dollars)，由each mile of the interstate route cost about 2million（or 0.002billion） to build 判定x和y呈现线性关系，且slope=0.002, 当x=2500miles时, y=5billion=0.002*2500, 因此y=0.002x，y-intercept=0，选A