1. 1) 3rd grader says: “A”
  2. 2) Adult says: “Mercury”
  3. 3) 3rd grader says: “Diamond”
  4. 4) Adult says: “206”
  5. 5) 3rd grader says: “12”
  6. 6) Adult says: “All of them have mass”
  7. 7) Adult says: “Crust”