A riboside is `:`

Options

A. Base + Phosphate
B. Ribose + Phosphate
C. Ribose + Phosphate + Base
D. Ribose + Base.

Answer

To answer the question "A riboside is:", we can break down the components involved in the formation of a riboside step by step.

### Step-by-Step Solution:

1. **Understanding the Components**:
- A riboside is formed from two main components: a nitrogenous base and a sugar.

2. **Identifying the Sugar**:
- In the case of a riboside, the sugar is specifically ribose. Ribose is a five-carbon sugar (pentose) that is a crucial component of RNA.

3. **Identifying the Nitrogenous Base**:
- The nitrogenous base can be one of the following: adenine, guanine, cytosine, or uracil. These bases are classified as either purines (adenine and guanine) or pyrimidines (cytosine and uracil).

4. **Combining the Components**:
- When a nitrogenous base (either a purine or a pyrimidine) combines with ribose, it forms a nucleoside. However, if we are specifically discussing ribosides, we are referring to the combination of ribose with a nitrogenous base.

5. **Conclusion**:
- Therefore, a riboside is defined as a compound that consists of ribose sugar bonded to a nitrogenous base.

### Final Answer:
A riboside is a compound formed by the combination of ribose sugar and a nitrogenous base.

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