Multiple choice

Starfish feeds on animals covered with hard shells. What is that hard shell made of?

  1. Sodium carbonate

  2. Calcium carbonate

  3. Potassium carbonate

  4. Calcium hydroxide

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The hard shell of sea animals is made of a chemical compound called calcium carbonate that protects them from mechanical injury.