Which of the following tables can be generated from the equation y = 2x + 1?
a: x y
2 1
3 2
4 3
5 4
b: x y
-4 1
-2 -1
0 -3
2 -5
c: x y
1 3
2 5
3 7
4 9
d: x y
0 3
1 5
2 7
3 9