For a fixed amount of an ideal gas at constant temperature, which plot is a straight line passing through the origin?

Boyle's law gives $PV=k$, so $V=k(1/P)$: a plot of $V$ against $1/P$ is a straight line through the origin with slope $k$. $V$ versus $P$ is a hyperbola and $PV$ versus $P$ is a horizontal line that does not pass through the origin.