Answer:
actually, a and b are correct, as any line is also parallel to itself (a).
b is probably the truly wanted answer, as this line is on a chart visible as a second line and parallel to the first one.
Explanation:
the factor of x is also the slope of the line.
for a line to be parallel to another, both need to have the same slope.
the constant number in the equation is the offset of the line from point (0,0) in y direction.
so, b is a parallel line 4 units above the first line.