To finance the purchase of a house from Tuna, Uri signs an instrument promising to pay to "Verity Mortgage Service" $160,000 with interest in installments with the final payment due July 10, 2040. To be negotiable, this instrument must include the signature of

a. a non-party witness.
b. Tuna or Tuna's realtor.
c. Uri.
d. Verity's chief financial officer.