General equation of line is [tex]y=mx+n[/tex] where m is slope and n is point on y-axis. So just use points in question to determine what m and n must be. Let me show you.
For A(0,1), put this point in [tex]y=mx+n[/tex] then you have [tex]1=m.0+n[/tex] Hence [tex]n=1[/tex]
Now use second one that is B(1,5), then you get [tex]5=m.1+1[/tex] since [tex]n=1[/tex]. Finally you get [tex]m=4[/tex] that is slope.
So you are right. It is D
