Which one of the following is not a property of classical smog?

Options

A. Occurs at low temperature
B. Secondary pollutant play significant role
C. does not Contain `SO_(2)`
D. Dark brown coloured

Answer

To determine which of the following is not a property of classical smog, let's analyze each option provided:

1. **Occurs at low temperature**: Classical smog is known to occur in cold and humid climates. This is a characteristic property of classical smog. Therefore, this statement is true.

2. **Secondary pollutants play a significant role**: Classical smog primarily consists of primary pollutants, such as sulfur dioxide (SO2) and particulate matter, which are directly emitted from sources like burning fossil fuels. Secondary pollutants, such as ozone, are not significant in classical smog. Thus, this statement is false regarding classical smog.

3. **Does not contain SO2**: Classical smog is characterized by a high concentration of sulfur dioxide (SO2). Therefore, this statement is also false.

4. **Dark brown color**: Classical smog typically has a dark brownish color due to the presence of particulate matter and other pollutants. This statement is true.

After analyzing all the options, we can conclude that the statement that is not a property of classical smog is:

**Answer: Secondary pollutants play a significant role.**