What type of card is typically used to express gratitude after a service?

The most appropriate answer is thank you cards, which are specifically designed to express gratitude, particularly following a service or after receiving support. These cards convey appreciation to those who attended the service, brought food, sent flowers, or offered condolences.

Acknowledgment cards, while related, are typically used to notify others about the passing and the arrangements rather than expressing thanks. Condolence cards are intended for offering sympathy to the bereaved rather than for expressing gratitude from them. Sympathy cards, similarly, are used to convey condolences rather than to thank those who have extended their support. Thank you cards specifically fulfill the purpose of expressing thanks after a service, making them the clear and suitable choice in this context.