Flammable liquids are those that have a flashpoint of:

• A. above 93.3^ext{o}C (200^ext{o}F)
• B. exactly 60^ext{o}C (140^ext{o}F)
• C. between 100^ext{o}C and 150^ext{o}C
• D. below 37.8^ext{o}C (100^ext{o}F)

Answer: (D)

Verified step by step guidance

1. Understand the definition of flashpoint: it is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid.
2. Recognize that flammable liquids are classified based on their flashpoints, which indicate how easily they can catch fire.
3. Recall that liquids with lower flashpoints ignite more easily and are considered more hazardous.
4. Note that the standard classification for flammable liquids is those with flashpoints below 37.8^\text{o}C (100^\text{o}F).
5. Therefore, the correct answer is that flammable liquids have a flashpoint below 37.8^\text{o}C (100^\text{o}F).