The question asks us to identify the person who is not a moderate. A moderate, in this context, refers to someone who adopts a middle-ground position and does not advocate for extreme measures.

Option 1: Pherozeshah Mehta - He was one of the prominent moderate leaders during the Indian National Congress`s early years. He believed in peaceful negotiation and constitutional methods to achieve political reforms.

Option 2: Surendranath Banerjee - He was also a moderate leader and a prominent figure in the Indian National Congress. He advocated for moderate reforms and sought to unite different factions within the Congress.

Option 3: Womesh Chandra Bonnerjee - He was the first president of the Indian National Congress and considered to be a moderate. He focused on constitutional and administrative reforms rather than radical changes.

Option 4: Bal Gangadhar Tilak - This is the correct answer. Tilak was not a moderate. He was part of the extremist faction within the Indian National Congress and advocated for more aggressive approaches, including agitation and mass movements.

Therefore, the correct answer is Option 4. Bal Gangadhar Tilak is not a moderate.