Final answer:
Carbon, hydrogen, and nitrogen are all elements, which are basic chemical substances that cannot be decomposed into simpler substances. They are fundamental in forming macromolecules like proteins and nucleic acids. The correct answer is b. elements.
Step-by-step explanation:
Carbon, hydrogen, and nitrogen are all examples of elements. Each of these is a basic chemical substance that cannot be broken down into simpler substances through chemical reactions. While compounds are composed of two or more elements, these substances are not compounds but rather individual elements.
Within biological systems, these elements are crucial components. For example, carbon is a fundamental component of macromolecules, such as proteins, nucleic acids, carbohydrates, and lipids. Carbon's ability to form up to four covalent bonds makes it a versatile backbone for these macromolecules.
Nitrogen is also a significant element in organic compounds and accounts for a large part of a cell's composition, especially as a component of proteins and nucleic acids.
Considering the examples provided, such as glucose, which has a ring that includes carbon atoms, shows us the importance of these elements in forming complex organic molecules.
Hydrogen is commonly bonded to carbon and is part of water and many organic compounds, while nitrogen plays a key role in the structure of amino acids and nucleic acids.
The correct answer to the question is b. elements.