Fossil fuel combustion increases the acidity of rain because

carbon dioxide dissolves in rainwater

sulfuric acid and nitric acid dissolve in rainwater

tiny particles of carbon dissolve in rainwater

sulfur dioxide and nitrogen oxides dissolve in rainwater

The second answer would be correct.

When fossil fuels combust, compounds such as NOₓ (Nitrogen Oxides) and SO₂ (Sulfur Dioxide). These compounds can then react with the environment to form the acids sulfuric acid and nitric acid, which, when reacted with water, release H₊ ions. The higher the concentration of H₊ ions, the more acidic the solution.

sulfur dioxide and nitrogen oxides dissolve in rainwater

Explanation:

The burning of fossil fuels leads to the emission of sulphur dioxide and nitrogen oxides. These are an acid gases. They dissolve in water to give acids. These acids lower the pH of rain water.

Hence in areas with high emission of burning of fossil fuels, the rain fall is likely to be acidic. Acid rain has many deleterious effects such as damage to roofing sheets, sculptures and paints of buildings as well as affecting the pH of natural water bodies.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.