"One of the causes is the sudden release of methane present in seabeds" You mean "one possible cause among many" (including, ATW, meteor impact, volcanism, se

"One of the causes is the sudden release of methane present in seabeds" You mean "one possible cause among many" (including, ATW, meteor impact, volcanism, sea level change, sea oxygen content change, sea acidity change). That doesn't make it one of THE causes. The word "possible" needs to be in there. There's no conclusive evidence for any of these.