In animal development, cells gradually become specialized through processes known as specification and determination. These stages dictate how cells commit to their future roles in forming tissues and organs.

Statement A highlights that during commitment, cells may not differ visibly from neighbors, but their developmental fate is restricted. This is correct because cells become committed internally before morphological differentiation becomes apparent. They are prepared to follow a specific developmental path even without outward changes.

Statement B says that at the specification stage, commitment is not labile (i.e., it is irreversible). This is incorrect. During the specification stage, commitment is labile or reversible, meaning cells can potentially change fate if environmental conditions vary. Irreversible commitment occurs later, at determination.

Statement C describes determination accurately. A cell or tissue is determined when it differentiates autonomously even when placed in different embryonic contexts or isolated, showing irreversible commitment.

Statement D involves cytoskeletal arrangements positioning nuclei in the syncytial embryo of Drosophila. This positioning enables specification via opposing morphogen gradients such as Bicoid and Caudal, which is accurate and crucial in early fruit fly development.

Statement E claims that capacity for mosaic development allows cells to acquire different functions through interactions with neighbors. This is false. Mosaic development is characterized by autonomous specification where cell fate is intrinsic and not reliant on interactions.

Therefore, the correct statements are A, C, and D, making option (4) A, C and D the right answer.

This article clarifies essential developmental biology concepts by dissecting stages of cell specification and determination. Understanding these principles is critical for grasping how embryos develop complex, organized bodies from seemingly uniform cells.