Which culture engaged in trade and built large cliff dwellings?

Which action allowed farming to be expand into west texas? a inventing a new plow b developing dry farming c increasing demand for cotton worldwide d declining of the cattle ranching industry

If a swimmer is traveling at a constant speed of 0.85 m/s,how long would it take to swim the length of a 50m olympic sized pool?

What were the death camps? who was sent there?