Which sitcom starring Lucille Ball and Desi Arnaz began on CBS in 1951 and became a rerun favorite for decades?

Which actor played Meryl Streep's troubled son in the 1996 film "Marvin's Room"? Around 1940, Howard Florey and Ernst Chain purified which antibiotic, discovered by Alexander Fleming in 1928? Before independence in 1966, Botswana was a British protectorate known by what name? What does "LP", the term for a vinyl album, stand for? Long before it named office machines, which job title described people like Johannes Gutenberg? Before its sighting in 1846, which eighth planet's existence was deduced from its gravitational pull on another planet? Before its completion in 1917, the Quebec Bridge collapsed twice during construction. Which river does it cross? Before Joe Montana played for the Kansas City Chiefs, which team did he lead to four Super Bowl titles?