It is not until the final period of prenatal development, the stage, that the developing child becomes easily recognizable.

The correct answer is the fetal stage.

 It is not until the final period of prenatal development at the fetal stage, where the developing child becomes easily recognizable. The fetal stage formally starts when differentiation of major organs occurs.
 It is also in the fetal stage where the child undergoes astoundingly rapid change and increases 20 times in size, for example, dramatic changes in weight and proportion. By three months the fetus urinates and swallows, hands and arms develop, nails and fingers develop.
 The Fetus is termed as the term for a developing child from eight weeks after conception until birth.

Cand d are correct because the rest are just showing your mistakes and you don’t want people who are reading a summary you wrote to see all the mistakes you made.