According to the proverb, a closed what catches no flies?

The Zytglogge, a clock tower with an astronomical clock from 1530, is a landmark of which Swiss capital city? Which director made "A Clockwork Orange", "Full Metal Jacket" and "Spartacus"? What is the name of the violent teenage narrator of "A Clockwork Orange"? What is a close-fitting, often strapless bodice called? A cloud of ash circled the Earth when most of which volcanic island was obliterated in an 1883 explosion? The Battle of Waterloo pitted which two great commanders against each other? Who co-founded the Black Panther Party? Which singer was a lead vocalist of Jefferson Starship?