Here are the possible answers based on the context:
* Linda was playing volleyball when she got the invitation card.
* Marie was writing when she got the invitation card.
* Pam was reading when she got the invitation card.
* Stuart was feeding when he got the invitation card.
* Tom was walking when he got the invitation card.
* Luc was listening to when he got the invitation card.
* Marc was taking photos when he got the invitation card.