The statement "All biomolecules have the following traits except" implies that one of the options listed does not apply to all biomolecules. The options listed are:
- Nitrogen elements.
- A carbon backbone.
- Hydrogen elements.
- Covalent bonds.
Among these, not all biomolecules contain nitrogen. For example, carbohydrates and lipids do not necessarily contain nitrogen, while proteins and nucleic acids do. Therefore, the correct answer is:
Nitrogen elements.