Question

1. dead echinoderms are naturally recycled to make which product?

○ they are the main ingredient in livestock feed.
○ they are the main ingredient in collagen.
○ they are the main ingredient in limestone.
○ they are the main ingredient in toothpaste.

Explanation:

Echinoderms (like sea urchins, starfish) have hard parts with calcium carbonate. When they die and decompose, their remains contribute to materials. Toothpaste often uses abrasives from such marine skeletal materials (from echinoderms and other marine organisms) for cleaning. Livestock feed main ingredients are usually grains/proteins, collagen comes from animal connective tissue, limestone is mainly calcium carbonate from various sources but not primarily echinoderms. So dead echinoderms are a main ingredient in toothpaste.

Answer:

D. They are the main ingredient in toothpaste.