Final answer:
In the novel 'Wonder,' Justin's 'gift' to Olivia for Valentine's Day is his presence and support at her school play which takes place around that holiday.
Step-by-step explanation:
In the book Wonder, Justin does not specifically give Olivia (also known as Via) a physical gift for Valentine's Day. Instead, their celebration of the holiday is mentioned in a more general context. Justin attends Olivia's school play, which is performed around Valentine's Day, indicating his support and affection for her. It is the time they spend together and his support for her endeavors that serves as a 'gift' in the spirit of Valentine's Day.