Which of the following statements about thermal radiation is always true?
A) A hot object emits more X rays than a cool object.
B) A hot object emits more radio waves than a cool object.
C) A hot object emits more total radiation than a cool object.
D) A hot object emits more total radiation per unit surface area than a cool object.
E) A hot object emits less total radiation than a cool object.
Answer: D