The best valuation technique to reduce the value of Karl's gross estate is C) Special use valuation on the CDs.
Special use valuation is a valuation method that determines property value on the basis of its “current use” rather than its “highest and best use.”
Special use valuation is permitted by the Internal Revenue Code (IRC) Section 2032A.
However, the special use valuation method is for real estate and not CDs.
Thus, the best valuation technique to reduce the value of Karl's gross estate is C) Special use valuation on the CDs.
Learn more about the special use valuation method at https://brainly.com/question/3925584