Well, we know that setting is location and surroundings, usually! Irony/sarcasm doesn't apply here, as it's usually in the form of dialogue or much more than those statements.Even if you were confused about tragic resolution, you know enough that there isn't anything particularly 'tragic' nor 'resolving' about this excerpt. So characterization seems best fit, giving an idea on the individual and their attire and how they are interacting with the other! But please, you're free to interpret it yourself in any case if doubtful upon my own.
The best answer to complete the sentence correctly is impulse.
Impulse is a sudden desire to react or do something as a result of that urge. It also serves as a motivation to complete a desirable activity. It is usually used when things come unexpectedly.
The pig rolled around in the mud and squealed.
I ate a fig from the fig tree in Aunt Martha's backyard.
"I dig!" My baby brother squealed as he shovelled some more sand out of the hole.
