Final answer:
The statement "If A, then B" is best described by option D: If A is true, then B must be true.
Step-by-step explanation:
The statement "If A, then B" is best described by option D: If A is true, then B must be true.
In a conditional statement, the relationship between A (the condition) and B (the consequence) is such that B is true only if A is true. If A is false, it does not determine the truth value of B. However, if A is true, then B must also be true.