The principle discussed in the problem highlights the importance of clarity in agreements. As per the principle, agreements lacking certainty or the ability to be made certain are void. This means that for an agreement to be valid, all its terms must be clear at the onset.
In the given facts, Dev Patnaik offers to sell his motorbike to Ila Nayak for either ₹31,000 or ₹30,000. The phrase "₹31,000 or ₹30,000" introduces uncertainty regarding the definitive selling price of the motorbike.
For a contract to be valid, terms including price should be clearly agreed upon by both parties without ambiguity. Here, there is no clear indication of the agreed price between ₹31,000 and ₹30,000. Therefore, the contract fails the requirement of certainty as stipulated by the principle.
Thus, applying the principle to the given facts, the appropriate answer is: This agreement is void for uncertainty since there is nothing to show which of the two prices was finally agreed.