Select the nucleoside
(I)Adenosine
(II) Uridylic acid (III)Uridine
(IV) Cytidylic acid

Options

A. I and II only
B. I and III only
C. III and IV only
D. II and III only

Answer

To solve the question of selecting the nucleoside from the given options, we need to understand the definitions of nucleosides and nucleotides.

### Step-by-Step Solution:

1. **Understand the Definitions**:
- A **nucleoside** consists of a nitrogenous base (either purine or pyrimidine) attached to a sugar (ribose or deoxyribose).
- A **nucleotide** is a nucleoside with one or more phosphate groups attached.

2. **Analyze Each Option**:
- **(I) Adenosine**:
- Adenosine is composed of the nitrogenous base adenine and the sugar ribose.
- Therefore, **adenosine is a nucleoside**.

- **(II) Uridylic acid**:
- Uridylic acid, also known as uridine monophosphate (UMP), contains uracil (the nitrogenous base), ribose sugar, and one phosphate group.
- Therefore, **uridylic acid is a nucleotide**.

- **(III) Uridine**:
- Uridine consists of the nitrogenous base uracil and ribose sugar.
- Therefore, **uridine is a nucleoside**.

- **(IV) Cytidylic acid**:
- Cytidylic acid, also known as cytidine monophosphate (CMP), contains cytosine (the nitrogenous base), ribose sugar, and one phosphate group.
- Therefore, **cytidylic acid is a nucleotide**.

3. **Conclusion**:
- From the analysis, we find that the nucleosides among the options are:
- (I) Adenosine
- (III) Uridine
- The nucleotides are:
- (II) Uridylic acid
- (IV) Cytidylic acid
- Thus, the correct answer is **first and third only** (Adenosine and Uridine).

### Final Answer:
The correct options are **(I) Adenosine and (III) Uridine**.

---