Laughing requires a lot of emotional intelligence and is a complex thing. Normally people laugh about funny things, but adversative events can also lead one to laugh.
In this question the mostly likely to be the correct answer is After watching the new comedy at the theater, Nadia and George laughed hysterically for hours.
After leaving the haunted house, Upon returning home from the hospital after their car accident and Due to the sad news are events that can also triggers hysterical laughing but this kind of incongruence can be related to stress or anxiety, so this would not be the best opener to complete the sentence.