Which of the following is classified as a Class A flammable?

Class A flammables are materials that are capable of igniting and burning at normal temperatures, and they possess a flash point of 100°F (37.8°C) or lower. Ether, being highly volatile and having a low flash point, fits the criteria for Class A flammable substances very well.

Acetone, ethyl alcohol, and methanol are also flammable but have varying properties regarding their flash points. While they are indeed flammable substances, ethers are typically more hazardous due to their propensity to form peroxides and their volatility, which can lead to increased risks in certain conditions. The correct classification within these materials hinges on their specific flash points and combustion characteristics, thereby making ether the most representative example of a Class A flammable among the options given.