What phrase indicates the timing of Isabel's arrival in relation to an event?

The phrase that best indicates the timing of Isabel's arrival in relation to an event is "about to." This phrase suggests immediacy and readiness, implying that her arrival is imminent and will occur very soon. It conveys the idea that she will be arriving at or just before a significant event takes place.

In contrast, the other options reflect different temporal relationships. "Just before" indicates that Isabel arrives shortly prior to the event, while "after" suggests she arrives once the event has already occurred. "During" means she would arrive while the event is ongoing, but it does not capture the anticipation of her imminent arrival. Therefore, "about to" effectively captures the sense of a forthcoming event and aligns with describing the timing of Isabel's arrival.