Why Do Political Parties Carefully Select Which Candidates Will Represent

Why do political parties carefully select which candidates will represent the party in an election?

A) Political parties get more money if they have a candidate who is attractive and intelligent.
B) They want to make sure their candidate is fully aligned with their platform and agenda.
C) Parties choose candidates who will be controversial so the media pays more attention to them.
D) They want to choose candidates who give them the best chance at winning an election.