Final answer:
Cephalopods secrete sepia, a melanin-containing ink, from an ink gland located between the gills for defense against predators. The correct answer is option b, Sepia.
Step-by-step explanation:
Most cephalopods, such as squids and octopuses, have an ink gland that secretes sepia, a dark fluid containing melanin, to confuse enemies. The correct answer to the question is option b. Sepia. This ink-like substance is used as a defensive mechanism, which can be expelled to create a smokescreen effect, allowing the cephalopod to either hide or distract predators and escape. The ink gland is strategically located between the gills and releases ink into the excurrent water stream, which can be quite effective during predatory attacks or escapes.