Solution:
Political parties play a very vital role in the making of laws. Laws are made after long discussions among the members of the Parliament. These members belong to various political parties and are thus bound to represent the party's interests. For a bill to become law, it has to be passed with a majority. Thus, political parties play a major role in making laws for the country, and no law can become a bill unless the majority of parties support it.Thus, both the Assertion and Reason are true, and the Reason is the correct explanation of the Assertion.