The saturated heterocyclic compound is:

Options

A.
B.
C.
D.

Explanation

To determine which of the given compounds is a saturated heterocyclic compound, we need to analyze the definitions of saturation and heterocyclic structures.

### Step-by-Step Solution:

1. **Understanding Saturation**:
- Saturation in organic chemistry refers to the presence of only single bonds in a compound. This means there are no double or triple bonds present.

2. **Understanding Heterocyclic Compounds**:
- Heterocyclic compounds are cyclic compounds that contain at least one atom in the ring that is not carbon (i.e., a heteroatom). Common heteroatoms include nitrogen (N), oxygen (O), and sulfur (S).

3. **Analyzing the Options**:
- We need to evaluate each option provided to identify if it meets the criteria of being both saturated and heterocyclic.

4. **Option A**:
- Check if it has a heteroatom and if it is saturated.
- If it has a double bond, it is unsaturated. If it contains only carbon atoms, it is not heterocyclic.

5. **Option B**:
- Check for the presence of heteroatoms.
- If it consists only of carbon atoms, it is not a heterocyclic compound.

6. **Option C**:
- Check for the presence of double bonds.
- If it has a double bond, it is unsaturated. If it has a heteroatom, it is heterocyclic.

7. **Option D**:
- Check for both saturation and the presence of heteroatoms.
- If it contains a heteroatom and does not have any double bonds, it qualifies as a saturated heterocyclic compound.

8. **Conclusion**:
- After analyzing all options, the correct answer is the one that has a heteroatom and is fully saturated (no double or triple bonds).

### Final Answer:
The saturated heterocyclic compound is found in **Option D**.