In cities like Bombay and Calcutta the major air pollutants are

Options

A. Ozone
B. Carbon monoxide and oxides of Sulphur
C. Hydrocarbons and not air
D. Algal spores and marsh gas

Answer

### Step-by-Step Solution:

1. **Identify the Cities**: The question mentions two major cities, Bombay (now Mumbai) and Calcutta (now Kolkata), which are both metropolitan areas in India.

2. **Understand the Context**: These cities have high population densities and significant industrial activities. This leads to increased pollution levels due to various human activities.

3. **Consider the Sources of Pollution**:
- **Fossil Fuel Combustion**: The extensive use of fossil fuels for energy and transportation contributes to air pollution.
- **Automobile Exhaust**: With a high number of vehicles on the road, emissions from automobiles are a significant source of air pollutants.
- **Industrial Emissions**: Factories in these metropolitan areas release various pollutants into the air.

4. **Identify Major Air Pollutants**: The question provides options for major air pollutants. We need to analyze which pollutants are most relevant to these cities:
- **Ozone**: While ozone is a pollutant, it is primarily a secondary pollutant formed by reactions between other pollutants in the presence of sunlight.
- **Carbon Monoxide and Oxides of Sulfur**: These are direct emissions from vehicles and industrial processes.
- **Hydrocarbons**: These are also emitted from vehicles and industrial activities but are not as prominent as carbon monoxide and sulfur oxides in these cities.
- **Algal Spore and Mass Gas**: These are not typical major air pollutants in urban settings.

5. **Conclusion**: Given the extensive use of fossil fuels, automobile emissions, and industrial activities in Bombay and Calcutta, the major air pollutants in these cities are **carbon monoxide and oxides of sulfur**.

### Final Answer:
The major air pollutants in cities like Bombay and Calcutta are **carbon monoxide and oxides of sulfur**.

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