Looks like A and D <<<<-===== short answer.
In order for lines to be perpendicular the slope of one line has to be the minus reciprocal (upside down) of the other.
A
3x + y= 6
y = -3x + 6 So the second line has to be 1/3 Notice it is plus.
B
6x - 2y = 4
-2y = -6x + 4
y = (-6/-2)x + (4/-2)
y = 3x - 2
C
y = 3x - 2
D
y = 1/3 x +7