The main elements that all proteins, carbohydrates, lipids, and nucleic acids have in common are:

* Carbon (C)

* Hydrogen (H)

* Oxygen (O)

Additionally, most of these macromolecules also contain:

* Nitrogen (N) (present in proteins and nucleic acids)

* Phosphorus (P) (present in nucleic acids and some lipids)

Let's break down why:

* Proteins: Composed of amino acids, each containing a carbon, hydrogen, oxygen, and nitrogen atom.

* Carbohydrates: Made up of carbon, hydrogen, and oxygen. The ratio of hydrogen to oxygen is often 2:1 (like in water), leading to the general formula (CH₂O)n.

* Lipids: Diverse group but usually contain carbon, hydrogen, and oxygen. Some lipids, like phospholipids, also contain phosphorus.

* Nucleic Acids: Composed of nucleotides, which have carbon, hydrogen, oxygen, nitrogen, and phosphorus.

These four elements are essential building blocks for the structure and function of life. They form the backbone of these complex molecules, allowing for the creation of diverse and essential structures and functions within living organisms.