The correct option is B Eutherian mammals
Chances of survival of young ones are greater in Eutherian mammals (having placenta), because they are viviparous. Vivipary is both fertilization and development of the embryo inside the body of female with ensured nourishment for growing embryo by forming the placenta and giving birth to the young ones.
Fishes, aves and amphibians are all oviparous organisms i.e. egg laying animals. They are at a higher risk of predation and hence, lower chances of survival becuase of their development outside the parent's body.