Read this example paragraph. Coit Tower is one of San Francisco’s most interesting and best kept secrets. Since its completion in 1933, this tower on a hill has stood out from the San Francisco skyline. The tower was originally constructed as a memorial to Lillie Hitchcock Coit, a wealthy San Francisco resident who was well known for dressing like a man at a time when such things were frowned upon. In 1934, during the Great Depression, the federal government’s Works Progress Administration paid artists to paint murals on the walls of the tower. Many of those murals depict scenes of California life. Today, the tower is visited by only about 200,000 visitors a year, in contrast to the nearly 12 million visitors a year who flock to Fisherman’s Wharf. This makes Coit Tower an excellent spot to experience San Francisco’s charm while avoiding the commercial hustle and bustle of the big city.

Which sentence states the main idea of the paragraph?

the topic sentence, which indicates that Coit Tower is both interesting and little known
the topic sentence, which indicates that Coit Tower was built on a hill
the supporting sentence that states that the tower was built as a memorial to Lillie Hitchcock Coit
the supporting sentence that states that many murals were painted on the tower’s walls