Core elements in biomolecules: Which statements correctly describe oxygen, nitrogen, and carbon as used in living systems?

Introduction / Context:
Carbon, nitrogen, and oxygen are central to biochemistry. Their bonding capabilities and prevalence underpin the structures of amino acids, nucleotides, carbohydrates, and lipids.

Given Data / Assumptions:

• Covalent bonding dominates organic chemistry.
• Stable isotopes of C, N, O possess protons and neutrons.
• These elements are abundant in biological macromolecules.

Concept / Approach:
Carbon forms four covalent bonds, enabling diverse backbones and rings. Nitrogen commonly forms three covalent bonds and bears lone pairs, contributing to basicity and hydrogen bonding. Oxygen typically forms two covalent bonds and is highly electronegative, central to hydrogen bonding and polarity. All three are ubiquitous in biomolecules and occur as nuclei containing protons and neutrons (with minor isotopic variations).

Step-by-Step Solution:
Evaluate bonding capability: covalent bonding is true for all three.Assess nuclear composition: protons and neutrons present in stable isotopes.Confirm ubiquity in biomolecules: proteins, nucleic acids, sugars, lipids contain C, with O and N widely represented.

Verification / Alternative check:
Periodic trends and standard biomolecular formulae (for example, C, H, O, N composition) corroborate these facts.

Why Other Options Are Wrong:

• Any single statement alone: Incomplete; all are correct.
• None: Contradicts basic chemical knowledge.

Common Pitfalls:
Overlooking hydrogen, phosphorus, and sulfur—also important but not part of this item’s focus.

Final Answer:
All of the above.