Final answer:
Business groups are the primary lobby in Texas, working to influence lawmakers' economic and business decisions.
Step-by-step explanation:
The type of group that makes up the bulk of the lobby in Texas is d. business groups. These economic interest groups are comprised of industries, corporations, and trade associations, like the National Association of Manufacturers. Their primary goal is to influence economic and business decisions that lawmakers make, such as advocating for fewer governmental regulations. By contrast, agricultural groups, while significant, do not make up the majority of lobbyists in Texas. Similarly, citizen groups and movements like the Tea Party, although they may have substantial influence, do not represent the majority of the lobbying efforts.