Answer:
We are asked to describe the half-life of the radioactive materials.
- Hence the 3rd option is correct
Answer:
The spectator ions is:
and 
Explanation:
The equation of reaction between H₂ SO₄ and KOH is:

Rewriting this equation as ionic;
![[2H^{+} + SO^{2-}_4 + 2K^+ +2OH^- \to 2K^+ SO_4^{2-} + 2H_2O ]](https://tex.z-dn.net/?f=%5B2H%5E%7B%2B%7D%20%2B%20SO%5E%7B2-%7D_4%20%2B%202K%5E%2B%20%2B2OH%5E-%20%5Cto%202K%5E%2B%20%20SO_4%5E%7B2-%7D%20%2B%202H_2O%20%5D)
Spectators ions are ions present on both sides of the ionic equation by the same quantity but do not take part in the net reaction.
I believe it's 6789 times 10^4. I could be wrong, due to the fact that I don't remember what's the definition of the scientific notion. I hope this helps, or at least gives you an idea! :D
Salt=compound, soda=liquid solution, aluminum foil=element, milk=colloid,
steel=solid solution