The most appropriate one-word substitution for the given group of words "A place where dead bodies are kept for identification" is Option 4: Either 1 or 2.

Here's an explanation of each option:

Option 1: Morgue - A morgue is a place where dead bodies are kept temporarily, typically in a hospital or forensic setting, for various purposes such as identification, autopsies, or investigations.

Option 2: Mortuary - A mortuary is a place where dead bodies are stored, prepared for burial or cremation, and where funeral services may be held.

Both options 1 and 2 refer to places where dead bodies are kept, and both can be used as substitutes for the given group of words. The choice between "morgue" and "mortuary" may depend on the specific context or regional usage. Therefore, Option 4, which includes either option 1 or 2, is the most appropriate choice.