Humidity in the air is measured with a hygrometer.
The last sentence is one, but almost the entire excerpt speak of fighting and winning to get that ideal political situation. This excerpt is all about the freedom from fear. That sounds like a call to arms, an encouragement to overcome fear and fight. The sentences leading to the last talks about how maintaining freedom involves fighting for it, and that the only way to stop the struggle (for human rights) is to win that fight.
C) At an angle
This is what the anwser is
In "the open window" by Saki. The character Framton decides to go to the Stappletons' house to relax because he has been extremely nervous and believes the countryside will help him relax. Framton waits for Mrs.. Sappleton but Vera comes first and they start a conversation in which he discovers about the tragedy. This works as a contradiction to his expected outcome and actually makes him even more nervous.
The whole incident goes against what Framton expected, therefore is considered a situational irony.
The phrase in which that contradiction seems reflected from Framton Nuttel's perspective is: "She rattled on cheerfully about the shooting and the scarcity of birds, and the prospects for duck in the winter. To Framton it was all purely horrible."
