Misc: what was mark twain's real name?

Questions

Every finalest in the 100-meter dash of the last four olympics, has been of what descent?

Every human first spent about half an hour as a single what?

Every photograph of an american atomic bomb detonation was taken by who?

Every square inch of the human body has an average of 32 million ______?

Which company, during the 1984 Super Bowl, aired what is considered one of the best commercials in TV history?