Step 1: Understanding the Concept:
Elasmobranchs (sharks and rays) and cephalopods have unique specialized anatomical structures within their reproductive tracts to protect their developing embryos.
Step 2: Detailed Explanation:
The nidamental gland (or shell gland) is a specialized secretory organ located in the oviduct of female elasmobranchs and cephalopods.
In oviparous species, it secretes a tough, protective proteinaceous egg case (sometimes called "mermaid's purse" in sharks) that encloses and shields the fertilized eggs during development.
Step 3: Final Answer:
Thus, the nidamental gland helps in the secretion of the egg case, which corresponds to option (B).