Step 1: Identify the provision.
The question is about Section 20 of the Arbitration and Conciliation Act, 1996, which deals with the place of arbitration.
Step 2: Party autonomy comes first.
Under Section 20(1), the parties are free to agree on the place of arbitration. So the first preference is always what the parties themselves decide.
Step 3: The fallback rule.
Section 20(2) provides what happens if the parties fail to agree. In that case, the arbitral tribunal decides the place of arbitration.
Step 4: What the tribunal must look at.
When the tribunal decides, it must have regard to the circumstances of the case, including the convenience of the parties. So convenience is a key guiding factor.
Step 5: Eliminate the wrong options.
The place where the contract was executed, the location of the subject matter, and the jurisdiction of the civil court alone are not the tests fixed by Section 20(2). The Act ties the decision to the circumstances and convenience, not these.
Step 6: Conclude.
Where parties have not agreed, the tribunal fixes the place having regard to the circumstances of the case, including the convenience of the parties.
\[ \boxed{\text{Circumstances of the case, including the convenience of the parties.}} \]