Section 39 Companies Act 2013 deals with allotment of securities. Minimum subscription for an offer must be received within:

1. Section 39(1) Companies Act 2013: 'No allotment of any securities of a company offered to the public for subscription shall be made unless the amount stated in the prospectus as the minimum amount has been subscribed AND the sums payable on application for the amount so stated have been paid to and received by the company by cheque or other instrument.' 2. Sub-section (3): if the stated minimum amount is not received within the period specified, money shall be returned within a period of 15 days from the closure of the issue. 3. SEBI ICDR Regulations specify the period (currently 60 days from date of opening of issue for book-built issues; minimum subscription = 90% of issue size). 4. Hence option A is correct (referring to SEBI's prescribed period). _Source: Companies Act 2013 (Act 18 of 2013), Govt. of India MCA — Companies Act 2013, Section 39; SEBI ICDR Regulations 2018_