Concept:A pressure group is an organised body of people who unite to pursue shared interests and influence public decisions.
Explanation:Pressure groups are formed when people come together because they have common goals or interests.
Members may come from different backgrounds, incomes, or opinions, but they share a common cause.
They use collective action to push the government or other authorities toward policies that favour their shared interests.
Therefore, the key feature is that all members have similar interests, not that they are rich, all think alike on everything, or always oppose the government.
Answer:C. have similar interests.