You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: YOU ARE SO FOXY! 
Clue: The foxglove plant is the main source of this medicine used as a stimulant  in damaged heart tissue
digitalis

Category: HOT SPOTS 
Clue: 43 consecutive days of 120º heat were recorded in this appropriately named Calif. valley
death valley

Category: ECO-FRIENDLY VAMPIRES 
Clue: The vampires hope for great things from the "clean" type of this, generator of half of the USA"S electricity

coal