An opossum's ability to play dead when approached by a predator is an example of what kind of adaptation

It is a behavioral adaptation. 

There are three types of adaptations:
Structural - body parts that help it survive (e.g. color, size, shape)
Physiological - systems present in an organism that allow it a special feature (e.g. venom, skin color changes)
Behavioral - an action that allows the organism to better survive

Glucose, also called grape sugar, blood sugar or corn sugar, is among the simplest and one of the primary naturally occurring sugars. produced naturally by plants as the primary photosynthesis product, it is heavily used by living beings as a main energy source and is necessary for cellular respiration. chemically, it is a monosaccharide carbohydrate and serves as a building block for complex sugars like starch.