Explanation:

- Sacred: This word typically refers to something regarded with reverence and respect, often due to religious or spiritual significance.

- Option 1: Scarce

- Meaning: Rare or insufficient in quantity or number.

- Relevance: Not directly related to the spiritual or holy nature of "sacred."

- Option 2: Valued

- Meaning: Considered to be important or have worth.

- Relevance: While sacred items may be valued, "valued" does not capture the spiritual or religious aspect.

- Option 3: Holy

- Meaning: Dedicated or consecrated to God or a religious purpose; sacred.

- Relevance: Holy is synonymous with sacred, often used in religious contexts.

- Option 4: Precious

- Meaning: Of great value; not to be wasted or treated carelessly.

- Relevance: Refers more to monetary or sentimental worth than to spiritual reverence.

Conclusion: The most appropriate synonym for "sacred" is "Holy."