Fred has six nieces, ages five to sixteen. He writes an order instrument for $$50$ that states "Pay to the order of my niece." The order instrument is

a$.$ nonnegotiable, because it is illegal to write an order instrument payable to a relative.

b$.$ negotiable.

c$.$ nonnegotiable, because the amount of money is less than $$500.$

d$.$ nonnegotiable, because there is no specific person identified.