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If `A → B` holds in a relation, augmentation lets you also conclude
AB → A
BAC → BC for any attribute set C
CA → BC for any C
DAC → B for any C, but never AC → BC
Answer & Solution
Correct answer: B. AC → BC for any attribute set C
Augmentation rule: `A → B` implies `AC → BC` for any C. Same attribute added to BOTH sides. The other options either invert the arrow (impossible without more info), add C to only one side, or restrict to only the LHS — none match Armstrong's actual rule.
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