Final answer:
The question's answer is False (B). An argument with premises that are tautologies can still be valid if the premises logically entail the conclusion, as the validity of an argument depends on its logical structure.
Step-by-step explanation:
The question, "An argument all of whose premises are tautologies must be invalid," can be answered as False (B). A tautology is a statement that is true in every possible interpretation, so if all the premises of an argument are tautologies, they are true by definition. The validity of an argument is about the logical structure and whether the conclusion logically follows from the premises. A valid argument with true premises will always have a true conclusion. However, an argument can still be invalid if the premises are true but the conclusion does not logically follow from them. Since tautologies are always true, an argument constructed solely on tautologies can be valid if the premises logically entail the conclusion.