The question between 'a' and 'b' is whether such a deed is forged or not. 'A' affirms that it is genuine, 'B' affirms that it is forged—

• A. A statement by 'B' that the deed is genuine can be proved by 'A' and 'A' may prove a statement by 'A' that the deed is forged.
• B. A statement by 'A' that the deed is forged may be proved by 'A' and any statement by 'A' that the deed is genuine may prove by 'B'.
• C. 'A' can prove his statement that the deed is genuine
• D. 'B' can prove his statement that the deed is forged