The processes of calcination and roasting in metallurgical industries, respectively, can lead to:

First, we recollect what is meant by the two thermal treatments used in metallurgy:

$$\text{Calcination}$$ is the process in which an ore, generally a carbonate or a hydrated oxide, is heated in limited or no supply of air. The typical chemical change is the decomposition of a metal carbonate into its oxide with liberation of carbon dioxide gas. We state the generic equation:

$$\text{MCO}_3 \; \xrightarrow{\;\text{heat}\;} \; \text{MO} \;+\; \text{CO}_2$$

Now, carbon dioxide $$(\text{CO}_2)$$ is a well-known greenhouse gas. When it accumulates in the atmosphere it traps infrared radiation, producing the greenhouse effect. This effect raises the average temperature of the planet, a phenomenon commonly referred to as global warming. Hence, the chief environmental consequence of calcination is global warming.

Next, $$\text{Roasting}$$ is the process in which a sulphide ore is heated in excess of air so that the sulphide is converted into oxide with the simultaneous evolution of sulphur dioxide gas. The simplified form of the reaction is written as:

$$2\,\text{MS} \;+\; 3\,\text{O}_2 \;\xrightarrow{\;\text{heat}\;}\; 2\,\text{MO} \;+\; 2\,\text{SO}_2$$

Here, $$(\text{SO}_2)$$ escapes into the atmosphere. Sulphur dioxide is an acidic oxide. In moist air it is oxidised further and combines with water to form sulphurous and sulphuric acids as shown below:

$$\text{SO}_2 + \dfrac{1}{2}\,\text{O}_2 \longrightarrow \text{SO}_3$$

$$\text{SO}_3 + \text{H}_2\text{O} \longrightarrow \text{H}_2\text{SO}_4$$

These acids dissolve in atmospheric water droplets and fall back to the earth in the form of rain, popularly termed acid rain. Therefore, roasting contributes mainly to acid rain rather than to global warming or photochemical smog.

Putting both results side by side, we have:

• Calcination ⟶ liberation of $$\text{CO}_2$$ ⟶ global warming
• Roasting ⟶ liberation of $$\text{SO}_2$$ ⟶ acid rain

Among the given options, the pair “Global warming and acid rain” matches this sequence exactly.

Hence, the correct answer is Option B.