Question

Dr. Parmanu created a treasure hunt for his daughter Annu's 10th birthday. The last clue led her to a dog shelter where she would find her gift - a new puppy! The puppies at the shelter had numbered collars: Shiro
1
, Popo
2
, Candy
3
, Nacho
4
, Toto
5
, Nano
6
. The last clue was a piece of paper with the names of a few chemical elements: Sodium, Nitrogen, Oxygen.

Answer 1

2 popo

because sodium is a highly reactive metal and it produces pop sound when left in open air and it reacts with oxygen and nitrogen