Explanation:

- C. Rajagopalachari: He was a close associate of Gandhiji and an influential leader, but not known as his 'conscience-keeper'.

- Rabindranath Tagore: He respected Gandhiji and called him 'Mahatma', but wasn't called Gandhiji's 'conscience-keeper'.

- V. Patel (Vallabhbhai Patel): Patel was a trusted colleague, but not Gandhiji’s 'conscience-keeper'.

- G.K. Gokhale: He was Gandhiji’s political mentor and is often referred to as Gandhiji’s 'conscience-keeper', guiding him in matters of principle and policy.