What is generally a characteristic of substances like gasoline and alcohol?

The correct answer, C, highlights the characteristic of substances like gasoline and alcohol being volatile. Volatility refers to the tendency of a substance to vaporize. In the context of gasoline and alcohol, these substances easily evaporate at room temperature, releasing vapors that can ignite when exposed to an open flame or spark.

This property is crucial for understanding the behavior of these substances in both practical applications, such as fuel for vehicles, and safety contexts, where their flammability poses risks. Recognizing the volatility of gasoline and alcohol is essential for effective storage, handling, and ensuring safety measures are in place when working with them.

The other options do not accurately describe gasoline and alcohol. They are indeed flammable, meaning they can easily catch fire, which opposes the idea of being non-flammable. Additionally, they possess a high evaporation rate rather than a low one, making them readily turn into vapor. Lastly, both gasoline and alcohol are not heavy solids; instead, they are liquids at room temperature that have low densities compared to many other liquids. Understanding these traits emphasizes the importance of proper safety practices when working with volatile substances.