Which one of the following is not a negotiable instrument?

A Will is a testamentary document that takes effect only after the death of the testator and cannot be transferred during one's lifetime. Negotiable instruments like promissory notes, cheques, and bills of exchange are transferable instruments that represent a sum of money and can be negotiated (transferred) by delivery or endorsement. A Will lacks this essential characteristic of free transferability during the lifetime of its creator.