What is the augmented matrix for the given system of linear equations?

a. 1 2 3 | 4
3 4 5 | 6
6 7 8 | 9

b. 1 2 3 | 4 5
3 4 5 | 6 7
6 7 8 | 9 10

c. 1 2 3 | 4
0 1 1 | 2
0 0 1 | 3

d. 1 0 0 | 4
0 1 0 | 2
0 0 1 | 3