Step 1: Analyze the definition of Boolean Algebra.
Boolean algebra is a branch of algebra in which the values of the variables are the truth values \textit{true} and \textit{false}, usually denoted 1 and 0 respectively.
Step 2: Evaluate the options.
(A) Truth: While it deals with truth values, this is a component of the broader concept.
(B) Logic: Boolean algebra is the mathematical foundation of digital logic and computer science. It operates on logical statements.
(C) Symbol: It uses symbols, but this is true of all algebra, not its fundamental basis.
(D) Numbers: It uses the numbers 1 and 0, but they represent logical states (true/false), not numerical quantities in the traditional sense.
Therefore, Boolean algebra is fundamentally based on logic.