Answer;
-Carbon, because it can bond with many elements to form complex molecules.
Step-by-step explanation;
-A compound found mainly in living things is known as an organic compound. Organic compounds make up the cells and other structures of organisms and carry out life processes. Carbon is the main element in organic compounds, so carbon is essential to life on Earth.
-Living things need carbon in order to live, grow, and reproduce. Carbon is a finite resource that cycles through the Earth in many forms. This makes carbon available to living organisms and remains in balance with other chemical reactions in the atmosphere and in bodies of water like ponds and oceans.