The correct answer to what would this situation exemplify is B. Irony.
When, <em>after already struggling</em>, the man succeeds in building a fire <em>only to have it destroyed buy snow that suddenly falls</em> from a tree without any apparent reason, but only <em>by destiny's force</em>, an example of irony can be observed. An irony can be a synonym of <em>mockery or satire</em>. It is, by definition, <em>"a state of affairs or an event that seems deliberately contrary to what one expects"</em>. The man in the story probably felt relieved after struggling and being able to build a fire and <em>overcome his obstacles</em>, and <em>the last thing he must have expected</em> at the moment would be the fire's destruction. It configures a <em>mockery or satire event orchestrated by a destiny</em> that must have shattered the man's expectations. Therefore, the correct answer would be B. Irony.
The correct answer couldn't be <em>A. Falling action</em>, because a falling action is a <em>moment in a story right after the climax and right before the end</em>. The climax is t<em>he resolution of the main problem</em> in a story. The situation presented <em>doesn't show a resolution to the man's problems</em>, on the contrary, which doesn't allow it to exemplify the moment of falling action. Thus, the correct answer couldn't be A. Falling action.
The correct answer couldn't be <em>C. Conflict</em>, because a conflict shows the <em>contrast or disagreement between two forces</em>, usually a protagonist and an antagonist. In the situation presented, there is only a man struggling with destiny's mischief, but there is <em>no sign of an element that would involve two instances in a disagreement or even the presence of obstacles</em> that should be overcome. Actually, after having fallen into the water and overcoming an obstacle, the man was surprised by an unexpected situation, which configures irony. Hence, the answer couldn't be C. Conflict.
The answer couldn't be <em>D. Imagery</em>, because an imagery is <em>a descriptive or figurative language work that conveys visual symbolism</em>. There is <em>no apparent symbolism</em> in the situation presented, just its rawness, which is very real. <em>There isn't figurative language</em> in the situation. Therefore, the answer couldn't be D. Imagery.