Explanation

Mango (Mangifera indica) typically ripens in Pakistan from May to September, with peak harvest in June-August. However, the question asks for the 'period of ripening of seeds', which is biologically incorrect as mangoes are fruits that contain seeds; they do not have a separate seed ripening period distinct from fruit maturation. Assuming it means fruit ripening/harvest season, September-October (D) covers late-season varieties like Sindhri and Chaunsa in some regions, but July-August (A) is the peak for most common varieties. Given typical agricultural calendars in Pakistan, A is actually the most accurate for peak harvest/ripening.