Which of these parties could be called a single issue party?
a) the democratic party
b) the republican party
c) the libertarian party
d) the right-to-life party

D) the Right-to-Life Party

Explanation:

The Right-to-Life Party could be called a single issue party. As the name implies, it is centered on issues relation to the debate over abortion. The Democratic and Republican parties are major parties and have a wide range of issues and likewise the Libertarian Party also has a wide range of issues.