A contract contains the following provision: Jeremiah Johnson promises to pay $100,000 to Duke Ellis for renovations done on his house provided that Jeremiah may have an independent contractor come in and ensure that all of the renovations have been completed to Jeremiah's satisfaction. This provision:
a. cannot be valid since it makes Jeremiah's duty to pay dependent upon the inspection of a third party.
b. cannot create a valid condition, because it lacks the necessary words on condition that.
c. renders the contract unenforceable, because Jeremiah's promise is illusory.
d. creates an express condition precedent which must be met before Jeremiah's duty to pay arises.