The answer is: D
Explanation
The correct option is D: shall be made by majority of its members.
This is because Section 29 of The Arbitration and Conciliation Act, 1996 states that "[u]nless otherwise agreed by the parties, in arbitral proceedings with more than one arbitrator, any decision of the arbitral tribunal shall be made by a majority of all its members". This means that the arbitral tribunal can decide the dispute by a simple majority vote of the arbitrators, unless the parties have agreed on a different rule. Option A is incorrect because it implies that the arbitral tribunal must have a unanimous decision, which is not required by the Act. Option B is incorrect because it suggests that the arbitral tribunal needs a supermajority vote of two-thirds of the arbitrators, which is also not required by the Act. Option C is incorrect because it implies that the chief arbitrator has the sole authority to decide the dispute, which is not the case under the Act.