Which of the following best describes the term 'Labile' as it relates to organic substances?

The term 'labile' in the context of organic substances refers to materials that are easily altered, broken down, or destabilized. This characteristic indicates a susceptibility to change, whether due to environmental conditions such as temperature or pH, or through chemical reactions.

In many instances, labile compounds may be unstable and can undergo decomposition or transformation relatively quickly compared to more stable counterparts. This is particularly important in fields like biochemistry and pharmaceuticals, where the stability of organic compounds can significantly impact the efficacy and longevity of a substance.

The other options describe properties contrary to what 'labile' signifies. For example, being stable under all conditions or resistant to changes would define a substance that is robust and enduring, not easily altered. Rapidly synthesized without alteration suggests a process of creation rather than vulnerability, which again would not align with the properties of being labile.