A dominant two-party system means that in a political system, two political parties have a strong hold over the country's political landscape, and their candidates are the most likely to win elections.
Out of the options provided, the United Kingdom and United States operate a dominant two-party system. In the UK, the two dominant parties are the Conservative Party and the Labour Party. In the US, the two dominant parties are the Republican Party and the Democratic Party.
India and Pakistan, France and Germany, and South Africa and Senegal do not operate a dominant two-party system, as there are multiple political parties with a significant presence in their respective political landscapes.