ACID RAIN is formed when -(1) is DISSOLVED in water vapour, forming ...(2).... 1: carbon monoxide; 2 carbonic acid 1: carbon monoxide; 2 sulfuric acid 1: sulfur dioxide. 2 sulfunc acid 1. sulfur dioxide; 2 carbonic acid

## Step 1:Firstly, we need to understand how acid rain is formed. Acid rain is formed when air pollutants, such as sulphur dioxide (SO2) and nitrogen oxide (NOx), react with water vapor. Typically, factories and power plants emit large proportions of these gases into the atmosphere. ## Step 2:The pollutants (SO2 or NOx) missible in water vapor easily, producing acids through every reaction amongst different compounds. ### ### By inferring the above chemical reactions, it's understood that SO2 reacts with water vapor to form sulphuric acid or sulfunic acids--but not carbonic acid. ## Step 3:After screening each option, the only reasonable argument to complete this sentence "ACID RAIN is formed when … sulphur dioxide (1) is dissolved in water vapor, forming sulfunic acid (2)." aligns best with our preliminary stipulation and surface-level analysis.