Option 1: Bhagat Singh - Bhagat Singh was indeed associated with the Lahore conspiracy case. He was one of the main leaders of the Hindustan Socialist Republican Association (HSRA) and was involved in planning and executing the Lahore conspiracy.
Option 2: Surya Sen - This option is correct as Surya Sen was not associated with the Lahore conspiracy case. Surya Sen was a revolutionary from Bengal and was involved in the Chittagong Armory Raid of 1930, not the Lahore conspiracy.
Option 3: Rajguru - Rajguru, along with Bhagat Singh and Sukhdev, was involved in the Lahore conspiracy case. They were all part of the HSRA and were charged with the murder of John Saunders, a British police officer, in Lahore.
Option 4: Sukhdev - Sukhdev was also involved in the Lahore conspiracy case. He, along with Bhagat Singh and Rajguru, was one of the main conspirators and played a significant role in the planning and execution of the conspiracy.
In conclusion, the correct answer is option 2 - Surya Sen, as he was not associated with the Lahore conspiracy case.