The Ghadar Movement was a revolutionary movement in the early 20th century aimed at overthrowing British rule in India. Option 1, Shyamaji Krishnavarma, was a prominent Indian nationalist but he was not directly associated with the Ghadar Movement. Option 2, M. N. Roy, was an Indian revolutionary but he was not specifically associated with the Ghadar Movement either. Option 3, Bhagat Singh, was a prominent figure in the Indian independence movement but he was not directly involved in the Ghadar Movement. Option 4, Lala Har Dayal, was indeed associated with the Ghadar Movement. He was one of the key leaders of the movement and played an important role in organizing and mobilizing Indian nationalists against British rule. Therefore, the correct answer is option 4.