At a partys national convention, who selects the ticket?

The presidential ticket is selected by the delegates. The delegates are sent from the states after the primaries have taken place, and they are pledged to a particular candidate.

For example, in the 2016 Republican National Convention, the ticket Donald Trump-Mike Pence was selected by 1725 delegates which trump had "earned" during the primaries.

pepin the short[a] (german: pippin der kurze, french: pépin le bref, c. 714 – 24 september 768) was the king of the franks from 751 until his death. he was the first of the carolingians to become king.[b][2]

the younger son of the frankish prince charles martel and his wife rotrude, pepin's upbringing was distinguished by the ecclesiastical education he had received from the monks of st. denis. succeeding his father as the mayor of the palace in 741, pepin reigned over francia jointly with his elder brother carloman. pepin ruled in neustria, burgundy, and provence, while his brother carloman established himself in austrasia, alemannia and thuringia. the brothers were active in suppressing revolts led by the bavarians, aquitanians, saxons, and the alemanni in the early years of their reign. in 743, they ended the frankish interregnum by choosing childeric iii, who was to be the last merovingian monarch, as figurehead king of the franks.

honestly i love the walking dead, mainly the quotes. “well, pardon me young man, excuse the [insert bad word here] out of my gosh darn french, but did you just threaten me? ” sksk (of course it's not the exact words)