Choisissez l'option justeQuand deux personnes se marient, il y a un/une.

In the context of the question, when two people get married, the term that accurately describes this event is a marriage. A marriage is a formal union recognized by law, where two individuals usually vow to live together in a committed relationship. The other options listed do not correctly fit the scenario:

• Baptême: This is a baptism, a religious ceremony signifying spiritual cleansing and rebirth, not associated with people getting married.
• Accident: This refers to an unexpected and typically negative event, unrelated to marriage.
• Mort: This means death, which is unrelated to the concept of marriage.

Therefore, the correct option to describe the event when two people marry is mariage.