Step 1: Picture the scene.
A decree is being executed under the Code of Civil Procedure, 1908. The court attaches property of the judgment-debtor. Now a third party steps in and says, this property is mine, not the debtor's. We must find how the law handles this claim.
Step 2: Recall the relevant rule.
Order XXI Rule 58 of the CPC deals exactly with claims and objections to the attachment of property during execution.
Step 3: What does Rule 58 say?
It says that when a claim or objection is raised against the attachment of property, the court executing the decree shall itself proceed to decide that claim or objection.
Step 4: Understand the purpose.
This rule was designed to avoid sending people off to file long separate suits. The executing court settles all questions of right, title, and interest in the attached property right there, so execution is not delayed endlessly.
Step 5: Eliminate the wrong options.
Option A (the court that passed the decree must decide first) is wrong, since it is the executing court that decides. Option B (only after execution is over) is wrong, as the claim is decided during execution. Option C (a separate suit must be filed) is exactly what Rule 58 avoids, so it is wrong.
Step 6: Confirm the right answer.
The executing court itself adjudicates the third party's claim. That matches option D.
Step 7: Final answer.
\[ \boxed{\text{Shall be adjudicated by the executing court.}} \]