A class of drugs whose major action is a calming or depressed effect on the central nervous system is called:

I would think it would be Rocks and The Continent's Shape Because Back In the Pangea Period All the Continents Were Squeezed Together and What Caused That is the Tectonic Plates Moving Rapidly and The Rocks To and What Caused Them to Drift Apart Forming The Continents We Know Today Was Rocks, The Tectonic Plates's Movement Again, and The Shape The Continents Are Now May Cause The Pattern To Reverse Back Into Pangea Which Would Probably Kill Us All, But The Good News Is That Shouldn't Happen For a Long Long Time According To the USGS and May Not Even Happen For a 1000 More Years And We May Not Be Here Anymore By Then Cus of The Things that Can Destroy Earth Are Likely To Destroy It Before The Next 1000 Year Mark Hits So We Have a lot more to worry about right now than the Continental Drift Reversing. We have to worry about Yellowstone or Iceland's Volcano Erupting Because That Could Mean 100s of Thousands of People To Even Millions Would Be Killed and Both Options of Volcanoes Will Throw The World Into An Ice Age Not Too Long After The Eruption, but again we have way more things to worry about than A Supervolcanic Eruption and I know I am talking your head off but for 16 I know a lot about the World, Its Past, and Its Future!! :-) I hope that very long answer helped u and everyone understand Geology and Earth Science More Plus Climate Change, etc :-)