The spectator ions would be the ions that <em>don't </em>comprise the precipitate in this reaction. You have four ionic species here: Pb²⁺, NO₃⁻, H⁺, and SO₄²⁻. Since Pb²⁺ and SO₄²⁻ combine, as you are told, to form the precipitate, that leaves H⁺ and NO₃⁻ (or, in normal text, H+ and NO3-) to be the spectator ions.
Edit: NO3- might be interpreted ambiguously since it's not immediately clear that the NO3 is a polyatomic ion with a -1 charge and not an NO compound with a 3- charge, so it should be written as [NO3]- or (NO3)-.
The net ionic reaction shows the reaction without the spectator ions. In this case, that would be: Pb²⁺(aq) + SO₄²⁻(aq) → PbSO₄(s).
Nuclear fission because an atom is splitting in two fragments.
Chlorofluorocarbons are a class of organic compounds that were used as propellants in the late 20th century. The problem with CFC's is that they attack the ozone layer, breaking it down. The weakened ozone layer is not able to stop UV light from reaching the earth, so the amount of UV light reaching the earth increases. This results in increased temperatures, and the death of vegetation.
Therefore, the answer is B.
