1. The problem asks to identify the correct definition among the given options about logical statements. 2. Important definitions in logic: - A **tautology** is a statement that is always true, regardless of the truth values of its components. - A **contradiction** is a statement that is always false, regardless of the truth values of its components. - A statement that can be true or false depending on the values of its propositions is called a **contingency**. 3. Evaluate each option: - a. "A statement that is always false is called a tautology." This is incorrect because a statement always false is a contradiction, not a tautology. - b. "A statement that is always true is called a contradiction." This is incorrect because a statement always true is a tautology, not a contradiction. - c. "A statement that can be true or false depending on the values of its propositions is called a tautology." This is incorrect because such a statement is a contingency, not a tautology. - d. "A statement that is always true is called a tautology." This is correct. 4. Therefore, the correct definition is option d. Final answer: d. A statement that is always true is called a tautology.