Three substances normally considered as primary pollutant are ______,______,and,____.

Answer

To answer the question about three substances that are normally considered as primary pollutants, we can follow these steps:

### Step 1: Understand the Definition of Primary Pollutants
Primary pollutants are substances that are emitted directly from a source into the atmosphere. They are not formed by the reaction of other substances in the environment.

### Step 2: Identify Examples of Primary Pollutants
From the information provided, we can identify several examples of primary pollutants:
- Sulfur Dioxide (SO2)
- Nitrogen Dioxide (NO2)
- Carbon Monoxide (CO)
- Carbon Dioxide (CO2)
- Dichloro-Diphenyl-Trichloroethane (DDT)

### Step 3: Select Three Primary Pollutants
From the examples listed, we can choose any three to fill in the blanks. A common selection would be:
1. Sulfur Dioxide (SO2)
2. Nitrogen Dioxide (NO2)
3. Carbon Monoxide (CO)

### Final Answer
The three substances normally considered as primary pollutants are **SO2, NO2, and CO**.

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