Which of the following best describes how carbon skeletons can differ in organic molecules?

• A. They can only form straight chains with no branching or rings.
• B. They can only differ by the number of hydrogen atoms attached.
• C. They can only differ by the type of functional group attached.
• D. They can vary in length, branching, presence of $C_2$ double bonds, and ring structures.

Answer: (D)

Verified step by step guidance

1. Understand that carbon skeletons refer to the arrangement of carbon atoms in an organic molecule, forming the backbone of the structure.
2. Recognize that carbon atoms can connect in various ways: as straight chains, branched chains, or rings, which changes the shape and properties of the molecule.
3. Know that carbon skeletons can vary in length, meaning the number of carbon atoms can differ between molecules.
4. Be aware that carbon skeletons can include different types of bonds, such as single bonds or double bonds (e.g., C=C), which affect the molecule's reactivity and geometry.
5. Conclude that the diversity in carbon skeletons arises from variations in length, branching, types of bonds (single or double), and the presence of ring structures, rather than being limited to just one type of difference.