Step 1: Understand execution.
Execution under the CPC, 1908 is how a winning party gets the benefit of the decree. Order XXI governs it.
Step 2: See the problem.
When property of the judgment-debtor is attached, a third party may claim that the property is actually his, with independent title.
Step 3: Find the rule.
Order XXI Rule 58 lets the executing court itself investigate such claims and objections about attached property.
Step 4: Know what the court decides.
The court checks if the claimant has title, whether the property can be attached, and whether the attachment should continue or be released.
Step 5: Rule out wrong options.
No separate suit is needed, the claim need not wait till execution ends, and the decree-passing court need not decide it first.
Step 6: Final answer.
The claim shall be decided by the executing court.
\[ \boxed{\text{Shall be adjudicated by the executing court.}} \]