The correct option is **A. They are both composed of repeating monomer units.** ### Detailed Explanation: 1. **Understanding Polymers**: - Polymers are large molecules made up of repeating structural units called monomers. These monomers are covalently bonded together in long chains. - Both biopolymers (like proteins, nucleic acids, and polysaccharides) and synthetic polymers (like plastics such as polyethylene and polystyrene) share this fundamental characteristic of being composed of repeating units. 2. **Biopolymers**: - Biopolymers are naturally occurring polymers produced by living organisms. For example: - **Proteins** are made of amino acid monomers. - **Nucleic acids** (like DNA and RNA) are made of nucleotide monomers. - **Polysaccharides** (like starch and cellulose) are made of sugar monomers. - In each case, the properties and functions of the biopolymer are determined by the sequence and type of monomers used. 3. **Synthetic Polymers**: - Synthetic polymers are man-made and are created through chemical processes. For example: - **Polyethylene** is made from the monomer ethylene. - **Polystyrene** is made from the monomer styrene. - Just like biopolymers, the properties of synthetic polymers depend on the type of monomers and how they are arranged in the polymer chain. ### Why the Other Options Are Incorrect: **B. They are both exclusively formed through condensation reactions.** - This statement is incorrect because not all polymers are formed through condensation reactions. - While many biopolymers (like proteins and polysaccharides) are formed through condensation reactions (where water is released as monomers bond), synthetic polymers can also be formed through addition reactions (like in the case of polyethylene, where monomers add together without the loss of water). **C. They are both found only in natural environments.** - This option is misleading. Biopolymers are indeed found in natural environments as they are produced by living organisms. However, synthetic polymers are primarily man-made and are found in various environments, including urban and industrial settings. Thus, this statement does not hold true for synthetic polymers. **D. They both have a fixed molecular weight.** - This statement is incorrect because both biopolymers and synthetic polymers can have a range of molecular weights. - Biopolymers can vary in size due to the number of monomer units they contain, and synthetic polymers can also have different molecular weights depending on the polymerization process and conditions used. Therefore, they do not have a fixed molecular weight. ### Summary: - **Polymers** are made of repeating monomer units, which is a common feature of both biopolymers and synthetic polymers. - **Biopolymers** are naturally occurring and include proteins, nucleic acids, and polysaccharides. - **Synthetic polymers** are man-made and include plastics like polyethylene and polystyrene. - Not all polymers are formed through condensation reactions, and both types can have varying molecular weights. ### Revision Summary: - Both biopolymers and synthetic polymers consist of repeating monomer units. - Biopolymers are produced by living organisms, while synthetic polymers are man-made. - Not all polymers are formed through condensation reactions; some are formed through addition reactions. - Both types of polymers can have a range of molecular weights, not fixed values.