Powerful evidence from comparing iq test scores in many nations over time has shown that younger generations score higher because of:

The technological changes that we are experiencing in human society. With a little device that many carry in their pockets, individuals have the power to reach out to someone on the other side of the world. We are immersed in culture and ideas from around the globe. We have more opportunity to gather knowledge and use this knowledge, applying it to our general intelligence.

Icould be wrong but i would say b.

I'm going to go with 1,982 feet because of all of the ice.                                               ps its this is not the answer go with d 6,500.