Why did the French invade the German industrial region of the Ruhr in 1923?

AThe French believed the industrial area would help further its own economic recovery.
BThe Germans failed to maintain control over the area and radical factions were causing trouble there.
CThe French meant to force the Germans to continue paying the war reparations.
DThe Germans threatened to take back the Rhine region that was lost after the war, provoking a French invasion.