Step 1: Understanding the Question.
Under the provisions of Order 21 Rule 18 of the Civil Procedure Code, a decree-holder may apply for the execution of a decree. A joint decree, however, cannot be treated as a cross-decree in this case because the execution process applies only when a decree-holder is seeking enforcement of his own decree.
Step 2: Analysis of Options.
- (A) Mr. A may treat his joint-decree as cross-decree under Order 21 Rule 18: This is incorrect, as Mr. A cannot treat his joint-decree as a cross-decree.
- (B) Mr. A cannot treat his joint-decree as cross-decree under Order 21 Rule 18: This is the correct answer.
- (C) Mr. A cannot treat his joint-decree as cross-decree under Order 22 Rule 18: This is incorrect as Order 22 deals with substitution in cases of death and not the execution of decrees.
- (D) None of these: This is incorrect because option (B) is correct.
Step 3: Conclusion.
Thus, the correct answer is (B) Mr. A cannot treat his joint-decree as cross-decree under Order 21 Rule 18.