Which of these is the best statement about context clues?

AUsing context clues to decipher word meaning is effective when the writer provides ample information.

BUsing context clues to decipher word meaning is generally not as fast as using a dictionary.

CUsing context clues to decipher word meaning is the best choice in any situation.

DUsing context clues to decipher word meaning requires the reader to have knowledge of root words.