Simpson contracts with Perry Mason for legal services. While out of the country, Perry Mason assigns the contract to Saul Goodman, a lawyer with a poor record of legal advice. Which of these is the best argument that Simpson can make is that the contract cannct be assigned?

a. there is no argument against the assignment
b. because the assignment will materially increase the risk of nonperformance.
c. due to his failure to consent to the assignment.
d. due to the lack of consideration.