The correct option is A Viviparous
Vertebrates that lay eggs encapsulated in the shells or shell envelopes are referred to as 'oviparous'. Those vertebrates that gives rise to embryos without shells are viviparous. The resumption of viviparity has its own outcomes, i.e., their eggs become microlecithal, the egg shells are wanting a new organ; so placenta developed.
Thus, the correct answer is option (B).