To every linear transformation T from R2 to R2, there is an associated 2×2 matrix. Match the following linear transformations with their associated matrix.
1. Reflection about the x-axis.
2. Reflection about the line y=x.
3. Counter-clockwise rotation by π/2 radian.
4. Reflection about the y-axis.
5. The projection onto the x-axis given by T(x, y)=(x,0).
6. Clockwise rotation by π/2 radians.

a) 0 1
-1 0
b) 0 0
0 0
c) 0 1
1 0
d) 1 0
0 -1
e) 0 -1
1 0
f) -1 0
0 1