How did the storm begin?

The correct answer, which indicates that the storm began suddenly, suggests that the storm developed without any warning or gradual buildup. This implies an abrupt shift in weather conditions, catching people off guard and resulting in an immediate and possibly chaotic situation. Sudden onset storms are often characterized by a rapid increase in wind speed, a quick drop in temperature, or the appearance of dark clouds, which align with the idea of an event that occurs unexpectedly and without prior signs of change.

In contrast, the other choices imply varying degrees of gradual change or anticipation. For example, "gradually" suggests a slow development, while "quickly" still doesn’t capture the immediate and unexpected nature of the storm's arrival as well as "suddenly" does. "Unexpectedly" could also relate to how the storm caught people off guard, but it does not convey the immediate nature of its onset as directly as "suddenly." Therefore, the choice that best captures the nature of the storm's beginning is "suddenly."