Misc: What is the minimum number of bars on an abacus?

Questions

Since the beginning of the modern olympics, which are the only 2 countries to compete in them all (list alphabetically)?

Since Thomas Jefferson was a widower, who became unofficial first lady during his administration?

Single-celled fungus used to make beer & bread rise?

Skin is thickest where?

what term was defined as "far away from the ordinary"?