
Corinne P. answered 08/07/13
Vandy PhD Candidate: Boosting math-esteem while reducing math-scorn!
According to thefreedictionary.com, the "root of an equation" is "that value which, substituted for the unknown quantity in an equation, satisfies the equation." Therefore, choice A is the best answer.
Reference: http://www.thefreedictionary.com/Root+of+an+equation