when n=0, d(n)=690. This is the y-intercept All the functions given in the options are linear functions in the form y=mx+b, then we must find a function with independent term (y-intercept) b=690 The functions with b=690 are the first and third option.
For the slope (m), we can calculate it with 2 points of the table: n1=0, d(n1)=690 n2=2, d(n2)=560