Which document is executed with required formality to take effect upon a person's death?

The document that is executed with required formality to take effect upon a person's death is a will. A will outlines how a person's assets and liabilities will be distributed after their death, and it must be created according to specific legal requirements to ensure it is valid. This includes having the document signed and witnessed according to the laws of the relevant jurisdiction.

While a testament is a term often used interchangeably with a will, it is actually an older term that is less commonly used in contemporary legal contexts. A power of attorney is a legal document that grants someone authority to act on another person's behalf, typically while that person is still alive and incapacitated. In contrast, a living trust is an arrangement where assets are placed in trust while the person is alive and often continues after their death, but it does not serve the same specific purpose as a will for the distribution of assets after death. Thus, a will is specifically designed to take effect upon a person's death, making it the correct answer to this question.