What are the committee names for the counties with population between 50000-100000?
SELECT T2.Committee FROM county AS T1 JOIN election AS T2 ON T1.County_id   =   T2.District WHERE T1.Population  <  100000 AND T1.Population  >  50000
counties with population between 50000-100000 refers to WHERE Population < 100000 AND Population > 50000; committee names refers to SELECT Committee; JOIN is used to relate county table with election table on county id matching with district.