In May 1915, whom among the following did Gandhiji call as his political guru?

Mahatma Gandhi regarded Gopal Krishna Gokhale as his political guru (mentor). On returning from South Africa in 1915, Gandhi joined Gokhale's Servants of India Society and acknowledged Gokhale's deep influence on his political ideology — especially Gokhale's principles of moderation, constitutional methods, and dedicated public service. Gandhi famously said Gokhale was 'as pure as crystal, as gentle as a lamb, as brave as a lion'. Hence option (b) is correct.