Which statement reflects the core principle of the Best Evidence Rule's content requirement?

Which statement reflects the core principle of the Best Evidence Rule's content requirement?

• A. A copy of the writing is always sufficient to prove its content.
• B. Parol evidence is allowed to prove content even when the original exists.
• C. A summary of the writing can substitute for the original in any case.
• D. The original writing must be produced to prove its content unless an exception applies.

Answer: (D)