Answer:
C. national conventions for nominating presidential candidates
Step-by-step explanation:
The progressives wanted the citizens to have as much influence as possible during the election of the president.
If presidential candidates were chosen by the national conventions, the political parties are the one that will decide which person can run as the presidential candidates. The citizens/voters have no say on it. This will increase the risk that the parties will only appoint nominees that serve the interest of the party, not the citizens.
This is why the progressives favor direct primaries, which enable the citizens to vote for the candidate that should run for the presidential election.