The main system used by political parties to nominate the candidates in the modern political system of the US country is the primary system of elections.
Option A is the correct answer.
A political party is elected by the maximum votes given by the citizens of the country at the time of elections.
The primary method of elections is one of the techniques where the candidates are selected by casting votes through a secret ballot. But in some states, the system of the caucus is also used to elect a candidate for the party by organizing a meeting and having a discussion over that.
Therefore, the primary system of nominating the candidates in the political parties is used as one of its main methods.
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