N higher elevations, there is less . A. oxygen B. cloud cover C. sunlight D. precipitation

Can someone me? i need to have this done as soon as possible! i'm putting 20 points on this!

Iii-eneral sciencewhich of these is the best explanation of how a smooth round stone became smooth? a continuous freezing and thawingbvolcanic actioncit fell off the side of a cliffdit was in a stream for a long time.

What man-made lake was created by the building of the hoover dam?