During frog embryogenesis, the fate of prospective neurons shifts as the gastrula develops from early to late stages. Experiments transplanting prospective neurons into non-neural regions reveal critical differences in their developmental potential and specification:

• At the early gastrula stage, prospective neurons transplanted into the epidermis region fail to maintain their neuronal fate and instead differentiate as epidermis cells. This plasticity indicates that these early neurons are specified, meaning their fate is not yet fixed and can be influenced by environmental cues. Such behavior aligns with conditional specification, where cell fate depends on extrinsic signals and interactions.

• In contrast, prospective neurons from the late gastrula stage retain their neuronal identity even when placed in an epidermal environment. This reflects determination, where the cells have irreversibly committed to their neuronal fate and demonstrate autonomous development independent of external signals.

Combining these observations with the given statements:

(A) Early gastrula shows conditional development, while late gastrula demonstrates autonomous development — correct.

(B) The opposite scenario is incorrect.

(C) Early gastrula neurons are specified, late gastrula neurons are determined — correct.

(D) The reverse is inaccurate.

Thus, the correct conclusions are:

(2) A and C