A statement to the public "10,000 reward offered for information leading to the arrest of John Smith is _____.
a. A bilateral contract where a listener can accept by performance.
b. A unilateral contract where an offer can be accepted only by the listener's performance.
c. A unilateral contract where the listener can accept in writing only.
d. A contract that can be both bilateral and unilateral depending on the offeror's intent.