Most likely passage for the test:
Gas! GAS! Quick, boys!--An ecstasy of fumbling,
Fitting the clumsy helmets just in time,
But someone still was yelling out and stumbling
And flound'ring like a man in fire or lime--
Dim, through the misty panes and thick green light,
As under a green sea, I saw him drowning.
Context: From the Latin: Dulce et decorem est pro patria mori, sweet and fitting it is to die for one's country, the poem argues the opposite. The speaker witnesses a soldier dying in a gas attack. He argues if you saw what he saw, you would not tell the lie: dulce et decorum est pro patria mori.