DNA is conposed of repeating units of

Options

A. ribonucleosides
B. deoxyribonucleosides
C. ribonucleotides
D. deoxyribonucleotides

Explanation

**Step-by-Step Solution:**

1. **Understanding the Components of DNA**: DNA is a nucleic acid that is composed of smaller units called nucleotides. Each nucleotide is made up of three components: a phosphate group, a sugar molecule, and a nitrogenous base.

2. **Identifying the Type of Nucleotide**: The question specifically asks about the repeating units of DNA. While there are two types of nucleotides (ribonucleotides and deoxyribonucleotides), DNA is specifically made up of deoxyribonucleotides.

3. **Defining Deoxyribonucleotide**: A deoxyribonucleotide consists of:
- A phosphate group (H3PO4)
- A deoxyribose sugar (which is a five-carbon sugar with one less oxygen atom than ribose)
- A nitrogenous base (which can be adenine, thymine, cytosine, or guanine)

4. **Distinguishing Between Ribonucleotides and Deoxyribonucleotides**:
- Ribonucleotides contain ribose sugar, which has an -OH group on the second carbon.
- Deoxyribonucleotides have deoxyribose sugar, which lacks the -OH group on the second carbon, hence the prefix "deoxy."

5. **Conclusion**: Therefore, the correct answer to the question "DNA is composed of repeating units of" is **deoxyribonucleotides**.

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