​Amy and Bob Enter into a Contract for Bob to Perform

Multiple Choice

​Amy and Bob enter into a contract for Bob to perform waste management services for Amy's commercial properties. Later, Bob alters a material term-increases the price-without Amy's knowledge or consent. Amy

A) ​can alter a material term, such as the payment date, without Bob's consent.
B) ​can treat the contract as discharged.
C) ​must adapt his performance accordingly.
D) ​must determine whether Bob's alteration constitutes substantial performance.