The correct answer is (d). Raj Kumar Shukla was a peasant leader who played a key role in the Champaran Satyagraha. He was the one who first brought the plight of the peasants to Gandhi’s attention, and he was also one of the main organizers of the satyagraha.
Vallabhbhai Patel was a close associate of Gandhi’s, and he played a key role in many of his other satyagrahas, such as the Non-Cooperation Movement and the Quit India Movement. However, he was not involved in the Champaran Satyagraha.
Madan Mohan Malviya was a prominent Hindu nationalist leader who was also a close associate of Gandhi’s. However, he was not involved in the Champaran Satyagraha.
Shaukat Ali was a Muslim nationalist leader who was also a close associate of Gandhi’s. However, he was not involved in the Champaran Satyagraha.
The Champaran Satyagraha was a major turning point in Gandhi’s career. It was the first time that he had used satyagraha to successfully challenge the British Raj. The success of the satyagraha made Gandhi a national figure, and it also helped to spread the message of satyagraha to other parts of India.