Which equation represents a line that is perpendicular to the line represented by 2x-y=7?

the correct question is
Which equation represents a line that is perpendicular to the line represented by 2x - y = 7?

A. y = -1/2x + 6
B. y = 1/2x + 6
C. y = -2x + 6
D. y = 2x + 6

we know that
if two lines are perpendicular
so
the slopes
m1*m2=-1

we have 
2x-y=7-------> y=2x-7------------> slope m1=2

find slope m2
m2=-1/m1------> m2=-1/2

the slope m of the perpendicular line must to be -1/2
so

 the answer is
y = -1/2x + 6