The most useful piece of context to evaluate the events in this excerpt would be:
knowing whether it was common in this culture for mothers to choose wives for their sons.
This context is crucial because the narrative centers around Chên's mother's intentions to find a suitable match for her son, indicating the importance of familial involvement in marriage decisions in this culture. Understanding the norms regarding parental influence in betrothal would provide insight into the motivations and actions of the characters in the excerpt.