Explanation:

The correct answer is 2: 9% per annum. Under Sections 63 and 63A of the Transfer of Property Act, 1882, if no specific rate of interest is mentioned in the agreement, the default rate is fixed at 9% per annum. These sections apply in cases where compensation or reimbursement is payable concerning mortgaged property. Section 63 deals with compensation for improvements made by the mortgagee, and Section 63A pertains to improvements made by the mortgagor in possession. In both cases, the law prescribes this default rate unless otherwise agreed between the parties in the mortgage deed.