Which of the following best describes "earlier"?

The term "earlier" refers specifically to something that happened at a previous time in comparison to another event or point in time. The word "previously" aligns perfectly with this definition, as it conveys the sense of an action or event occurring before the current moment or before another specified time. This connection makes "previously" the most accurate description of "earlier."

The other options do not convey the same meaning. "Simultaneously" refers to events occurring at the same time, which is contrary to the concept of something happening earlier. "Afterward" denotes a time that follows a specific event or moment, which would not relate to the idea of "earlier." "Now" indicates the present moment, which again does not align with the notion of something that occurred in the past. Thus, "previously" is the appropriate choice to describe "earlier."