The poem "Dulce et Decorum Est" by Wilfred Owen explores the horrors and realities of war. It vividly describes the experiences of soldiers during World War I and highlights the different kinds of wars mentioned in the poem. These include:

a) War against humanity:
The poem portrays the brutality and inhumanity of war. It describes the gruesome effects of a gas attack on the soldiers, such as the "blood come gargling from the froth-corrupted lungs" and the haunting image of a fellow soldier dying in front of the narrator's eyes. This war against humanity is depicted through the suffering and dehumanization of the soldiers, who are reduced to mere shells of their former selves.

b) War against nature:
The poem also depicts the war against nature. It describes the harsh conditions in which the soldiers fight, such as the "haunting flares" and the "limping, blood-shod" soldiers marching through the mud. The poet highlights the contrast between the natural beauty of the countryside and the destruction caused by war. This war against nature symbolizes the disruption and devastation inflicted upon the natural world by human conflict.

c) War with gases and fire:
The poem emphasizes the use of chemical weapons, specifically gas attacks, during World War I. It vividly describes the effects of a gas attack on the soldiers, using powerful imagery to convey the horror and suffering they endure. The poem also mentions the use of fire, referencing the "green light" of flares and the "writhing in the wagon that we flung him in." This war with gases and fire represents the destructive power of modern warfare and its devastating impact on the soldiers.

d) All these:
The correct answer is option 'D' because the poem encompasses all of these different kinds of wars. It portrays the war against humanity, war against nature, and war with gases and fire. Through vivid descriptions and powerful imagery, the poem effectively conveys the horrors and realities of war, highlighting its impact on both the soldiers and the natural world.