Which of These Statements Is the Most Appropriate for Lighting

Which of these statements is the most appropriate for lighting a chroma-key background?

A) the lighting must be as even as possible
B) the light must be kept off the background as much as possible
C) the key light must have a yellow gel to counteract the blue
D) only small, precisely defined areas of the background should be illuminated
E) the background lighting must be at least six times the intensity of the foreground lighting