Step 1: Excavation timeline.
The Indus Valley Civilization sites of Harappa and Mohenjodaro were first excavated in the early 1920s.
Step 2: Role of John Marshall.
John Marshall was the Director General of the Archaeological Survey of India (ASI) from 1902 to 1928. During his tenure, systematic excavations at Harappa (Punjab, now in Pakistan) and Mohenjodaro (Sindh, now in Pakistan) revealed the existence of an advanced urban civilization.
Step 3: Elimination of wrong options.
- (A) Cunningham: He was the first Director General of ASI, but he worked earlier in the 19th century and did not excavate Harappa or Mohenjodaro.
- (B) S.R. Rao: Later archaeologist, known for excavating Lothal in Gujarat (a Harappan port town).
- (C) R.E.M. Wheeler: Came later (1940s) and re-examined Harappan sites with more modern techniques.
- (D) John Marshall: Correct, as he directed the first excavations of Harappa and Mohenjodaro in the 1920s.
Step 4: Conclusion.
Thus, John Marshall was the Director General of ASI during the excavation of Harappa and Mohenjodaro.