The embryonic development of Caenorhabditis elegans exemplifies the interplay between autonomous and conditional specification. The EMS blastomere, a critical founder cell at the 4-cell stage, generates two distinct cell lineages: MS (mesoderm) and E (endoderm). Its fate is not autonomously predetermined but influenced by signals from neighboring cells, especially the P2 blastomere.

Statement (A) is correct: Signals from the P2 blastomere instruct the EMS cell’s fate, indicating conditional specification where external cues guide fate decisions.

Statement (B) is correct: Without the instructive P2 signals, the EMS blastomere defaults to producing two MS cells, underscoring the default mesodermal fate in EMS absence of induction.

Statement (C) is incorrect: POP-1 functions as a transcriptional repressor promoting MS fate; its absence causes the prospective MS cell to adopt E fate, not vice versa.

Statement (D) is incorrect: MOM-2, a Wnt ligand from the P2 cell, induces E fate, not MS fate, through activation of the Wnt signaling pathway in EMS.

Hence, the combination representing the correct statements is:

(1) A and B

This highlights the importance of intercellular signaling pathways in defining cell fate during early embryogenesis. The successive induction events mediated by P2 and downstream effectors such as POP-1 and MOM-2 ensure proper establishment of the C. elegans cell lineage, balancing intrinsic cellular programming with extrinsic positional information.