Which one of the following is not a viviparous animal?
Camelus
Delphinus
Macropus
Ornithorhynchus
Prototherians (e.g., Ornithorhynchus) are oviparous mammals.
Metatherians (e.g., Macropus) and eutherians (e.g., Delphinus and Camelus) are viviparous.