Which lines are perpendicular?

Line A: y =
1
2
x + 2
Line B: y =
−1
2
x + 7
Line C: y = 2x + 4
Line D: y =
1
2
x +
5
4

Line A: y =
1
2
x + 2
Line B: y =
−1
2
x + 7
Line C: y = 2x + 4
Line D: y =
1
2
x +
5
4
Which lines are perpendicular?

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