What object did the ancient Roman architect Vitruvius relate to the perfect geometry of a circle and square?

The basic unit of stage lighting today is:

A. The electric incandescent bulb B. The limelight C. The carbon arc D. None of these choices

The country star who got his start at Sun Records and had several crossover hits, including "I Walk the Line," is

A. Johnny Cash B. Elvis Presley C. Jimmie Rodgers D. Hank Williams Sr.