A. endoskeleton
Endoskeleton is not a characteristic of Arthropods that has attributed to their diversity and success. Endoskeleton is defined as inner characteristics of the skeletal feature of an organisms such as bears, humans, fish and etc.
Exoskeleton on the other hand is the trait by which arthropods posses. It is skeletal feature that is described outside or is extrinsic, this is evident as crabs have their skeletons outside of their body.
I think the answer is enzyme
It's not alive, nor is it even an organic compound.
- It cannot respond to stimuli (Responsiveness)
- It cannot secrete hormones (Secretion)
- It cannot send messages along a nervous system or anything similar (Conductivity)
- It cannot break down compounds to usable energy forms (Digestion)
- It cannot absorb broken down compounds as an energy source (Absorption)
- It cannot reproduce (Reproduction)
- It cannot grow--it has no cells (Growth)
- It cannot exchange gases between cells (Respiration)
- It cannot rid itself of waste material (Excretion)
