Which tables could represent direct variation? Explain why. (Hint: What happens to $y$ if you multiply $x$ by a constant?)

1. $x$	$1$	$2$	$3$	$6$	$8$	$9$
   $y$	$2.5$	$5$	$7.5$	$15$	$20$	$22.5$

2. $x$	$2$	$3$	$4$	$6$	$8$	$9$
   $y$	$2$	$3.5$	$5$	$7$	$8.5$	$10$

   (a): If we multiply $x$ by $c$, $y$ is also multiplied by $c$.
   (b): If we increase $x$, we also increase $y$.
   None of the above