The decrease in the number of has been identified as one cause of increasing polarization.

Liberal republicans

Explanation:

In the discipline of politics, polarization is referred to as the state of the divergence of the governmental belief to the ideological ends. Most of the argument about the polarization in the discipline of the political science and dismal science tends to consider the polarization in the framework of the political organizations and the democratic structure of the federal government.

Here, in this particular case in United State there has been recorded a decrease in no. of liberal republicans which has been further identified as a cause of the increase in polarization.

your answer should be c, it seems to be the only one that makes sense. mark me branliest : )