Answer:
A. Gastrulating period is not a stage of prenatal development.
Step-by-step explanation:
Gastrulation is a very early stage in the development of embryo of most animals, during which single layered blastula is again organised to multiple layer structure which is known as gastrula. Development of three primary germ layers which happens during first two weeks of development. At this phase embryo is only a few mm long.Gastrulation happens after cleavage and development of blastula & primitive streak.During this time blastula is divided into three germ layers :- Ectoderm, mesoderm & endoderm.
Prenatal stages are divided into three stages: germinal, embryonic & fetal. Prenatal development is also divided into three trimesters that don't match with the three stages. The first two weeks after conception is known as germinal stage,the third through 8th week is known as embryonic and time from 9th week until birth is called fetal period.