Step 1: Understanding the Concept:
The Specific Relief Act, 1963 (amended in 2018), introduced the concept of "substituted performance" under Section 20.
Step 2: Detailed Explanation:
- Section 20(2) of the Act mandates that if a party seeks substituted performance (hiring a third party like 'C' to do the work), they must first provide a written notice to the party in default (B) requiring them to perform within a period of not less than 30 days.
- If the party (A) fails to provide this prior notice, they lose the statutory right to recover the additional costs incurred from the defaulting party (B).
Step 3: Final Answer:
Since 'A' did not give the mandatory notice required by the Act, 'A' cannot recover the additional ₹ 10 lakh. Option (B) is correct.