What should you do if a casualty has their first fit?

If a casualty has their first fit (seizure), the primary concern is ensuring their safety and providing the proper medical response. Notifying an ambulance upon arrival is crucial in this situation. This ensures that trained medical professionals can assess the individual appropriately since having a first fit may indicate an underlying medical condition that needs further investigation.

The other choices do not prioritize the immediate medical assessment and care that would be necessary for someone who has experienced a seizure for the first time. Advising rest might seem reasonable, but it does not address the need for professional medical evaluation. Instructing the individual to take medication might not be appropriate if they are unsure about their condition or if they have never been evaluated by a healthcare provider before. Sending them home could also be dangerous, as it would leave them without immediate access to medical help, which is particularly important if this was their first seizure.