Who has used the term ‘bowling alone’ to describe the erosion of community ties in the United States?

The correct option is Robert Putnam.

The term "bowling alone" was popularized by the American political scientist Robert Putnam. He first introduced it in a highly influential 1995 journal article titled "Bowling Alone: America's Declining Social Capital," which he later expanded into the bestselling book, Bowling Alone: The Collapse and Revival of American Community, published in 2000.
In his research, Putnam used the metaphor of bowling to illustrate a significant shift in American social behavior. He observed that while the total number of people who went bowling in the United States had increased over the latter half of the twentieth century, participation in organized bowling leagues had drastically declined. Instead of joining leagues and interacting with others, people were increasingly "bowling alone."

Putnam used this trend to argue that the United States has experienced a severe reduction in "social capital" — the social networks, norms of reciprocity, and mutual trust that bind a community together. The decline in league bowling, along with drops in participation in civic organizations, parent-teacher associations, and religious groups, points to a broader erosion of traditional community ties and active civic engagement since the mid-20th century.