The first name of the Spanish queen who funded Columbus's voyage was Isabella. She was Isabella I of Castile, who ruled alongside her husband, Ferdinand II of Aragon, as one of Spain's Catholic Monarchs.
In 1492, after the conquest of Granada, Isabella agreed to support Columbus's westward expedition. He hoped to reach Asia by sailing across the Atlantic, but instead reached Caribbean islands unknown to Europeans. The crown granted him ships, authority, and promised titles and rewards for the lands he claimed.
A common mix-up is answering Ferdinand, because he was also a monarch and co-sponsor of the expedition. However, the question asks for the queen's first name, making Isabella the single canonical answer. Her name is also commonly rendered Isabel in Spanish; English-language quizzes conventionally use Isabella.