Polymers are :

Options

A. large organic molecules linking together repeating subunits of the same type called monomers
B. found in proteins, carbohydrates, and nucleic acids
C. due to a dehydration reaction
D. all of the above

Explanation

### Step-by-Step Solution:

1. **Understanding Polymers**:
- Polymers are large organic molecules made up of repeating subunits known as monomers. These monomers are linked together through covalent bonds to form a larger structure.

2. **Identifying the Types of Polymers**:
- Polymers can be found in various biological macromolecules, including proteins, carbohydrates, and nucleic acids.
- For example, proteins are polymers made from amino acid monomers.
- Nucleic acids, such as DNA and RNA, are polymers formed from nucleotide monomers.
- Carbohydrates include polymers like starch, glycogen, cellulose, and chitin, which are made from sugar monomers.

3. **Dehydration Reaction**:
- The formation of polymers from monomers typically occurs through a process known as a dehydration reaction.
- In this reaction, when two monomers combine, a hydrogen atom from one monomer and a hydroxyl group from another monomer react to release a water molecule. This results in the formation of a covalent bond between the two monomers, leading to the creation of a polymer.

4. **Conclusion**:
- Since all the statements regarding polymers are correct, the answer to the question "Polymers are:" is **all of the above**.

### Final Answer:
**All of the above**

---