The equetion y = 9 and y = - 12 both are horizontal line that drawn at 9 unit above the origine and 12 unit below the origine respectively . So they are horizontal line which are parallel .
The equetion y = 9 and y = - 12 both are horizontal line that drawn at 9 unit above the origine and 12 unit below the origine respectively . So they are horizontal line which are parallel .And for the 2nd one all the choice are correct . but as we said before they are horizontal line that dawn passing through y-axis . So the 1st one is correct which is "ALL HORIZONTAL LINE ARE PARALLEL" .