The correct answer is 2. Siegfried Sassoon because he was a well-known British war poet and soldier during World War I who became famous for his outspoken criticism of the war.
In 1917, Sassoon wrote a letter titled "Finished with the War: A Soldier’s Declaration," which he sent to his commanding officer. In this letter, he expressed his belief that the war was being unnecessarily prolonged by those in power and accused the government of continuing the conflict for its own ends, rather than for any justifiable reason. The letter was read out in the House of Commons, which brought Sassoon significant attention.
Instead of facing a court-martial for his defiance, Sassoon was sent to Craiglockhart War Hospital in Edinburgh, where he was treated for shell shock (now known as PTSD). This was likely done to avoid the embarrassment and controversy of prosecuting a decorated war hero. During his time at Craiglockhart, he met fellow poet Wilfred Owen, and the two became close friends.
The other poets listed, such as Rupert Brooke, Wilfred Owen, and Isaac Rosenberg, were also significant war poets, but it was Siegfried Sassoon who gained notoriety for his explicit criticism of the war and the subsequent events that led to his being sent to Craiglockhart.