Explanation
Mohenjo-daro (in present Pakistan) and Harappa (in Punjab) were the two greatest urban centers of the Indus Valley Civilization, known for their grid-pattern streets and advanced drainage. Chronology narrows the alternatives before the individual names are compared. Mohenjo-daro and Harappa fits that evidence because it matches the specific chronology, agency and function contained in the question. A comparison with the alternatives is useful: Pataliputra and Taxila, Varanasi and Mathura and Ujjain and Kashi are genuine historical terms or names, but each belongs to a different office, patron, text, region or sequence. Reading the question as a relationship among person, period, place and institutional purpose prevents that mistake. The compact memory link is therefore Mohenjo-daro and Harappa together with the factual context above, not the isolated option letter.