In the first form of marriage described in the Manusmriti, the father gifts his daughter to a groom who is proficient in which of the following?

Learned in the Vedas.

The Manusmriti describes various forms of marriage, including the first, fourth, fifth, and sixth, as follows:

First: A father gifts his daughter to a knowledgeable man proficient in the Vedas. He dresses her in costly attire, honors her with valuable jewels, and personally invites the groom.
Fourth: A father gifts his daughter to the groom after addressing the couple with the words, "May both of you perform your duties together," and showing honor to the groom.
Fifth: The groom receives the maiden after providing as much wealth as he can afford to the kinsmen and the bride herself, according to his own discretion.
Sixth: A voluntary union between a maiden and her lover, arising from mutual desire.