USCoal Companies and Coal-Burning Utilities Have Suggested There Is Something

U.S.coal companies and coal-burning utilities have suggested there is something called clean-coal. Which of the following is false about clean coal?

A) stricter pollution controls will not stop release of some carbon dioxide
B) burning coal will always result in production of hazardous ash
C) one type of coal is significantly cleaner than other types
D) climate scientist James Hansen calls coal the single greatest threat to civilization
E) air pollutants will always be released by burning coal