The correct answers are A) people and D) party leaders.
Two convention delegates may be chosen by the people and party leaders.
In the United States convention delegates are selected at the state level. The Republican and Democratic committees follow rules and formulas to select their delegates, that are different, depending on each state. These delegates gathered in national conventions in June-July of every election year to select its candidate to the Presidency. The two basic methods that parties use to select their delegates that are going tp assist to the National Convention are the Primary and the Caucus.