Wonyoung: Hey, unnie-dul.
Nako: What is it?
Wonyoung: We just had lessons from Science class.
Yuri: Then?
Wonyoung: Yena-unnie and Yuri-unnie can't be together.
YenYul: EHHHH?
Yena: Why?
Wonyoung: A duck and a hamster can't "copulate".
Yena: ...
Yuri: ...
Nako: ...
Nako: Wonyoungie, excluding being animals, you also need to check the gender.