Step 1: Understanding the Concept:
The excavation of the Harappan site is a landmark event in the history of Indian archaeology. It was a collaborative effort involving several archaeologists over many years. The question asks for the starting year of excavation by Madho Swaroop Vatsa.
Step 2: Detailed Explanation:
The initial excavations at the Harappa site were started in 1921 under the supervision of archaeologist Daya Ram Sahni. Madho Swaroop Vatsa was a key archaeologist who worked alongside Daya Ram Sahni from the beginning of the major excavation campaign in 1921. He later continued the excavation work at Harappa in the following years, notably in 1926. However, his involvement began with the first major season of work in 1921. Therefore, 1921 A.D. is the most appropriate answer marking the beginning of his work at the site.
Step 3: Final Answer:
Madho Swaroop Vatsa began his excavation work at Harappa in 1921 A.D. along with Daya Ram Sahni. Thus, option (D) is the correct answer.