In which of the following groups of vertebrates is parental care mostly exhibited?

Parental care is mostly exhibited in the group of vertebrates known as Mammals. Mammals are a class of vertebrate animals that have several unique characteristics that make them well-suited to exhibit parental care. First and foremost, mammals give birth to live young, which requires a significant investment of time and energy on the part of the mother. Additionally, most mammalian mothers produce milk to feed their offspring, which requires further investment of energy and resources. Furthermore, mammalian offspring are generally born in a relatively undeveloped state and require a significant amount of care and nurturing in order to survive. This often involves extended periods of maternal care, as well as, in some species, the active participation of the father or other family members in raising the offspring. In contrast, while some birds (Aves) and some reptiles (Reptilia) exhibit parental care, it is generally not as extensive or prolonged as that seen in mammals. Amphibians (Amphibia), on the other hand, typically do not exhibit parental care beyond depositing eggs in suitable locations. Therefore, based on these characteristics, it can be concluded that parental care is mostly exhibited in Mammals.