According to the Uniform Securities Act, which of the following investment advisory practices is prohibited?
a. A client's portfolio increases in value from $100,000 to $150,000 over a one-year period, so the adviser charges the client a fee based on the total value of the account
b. An investment advisory firm appoints three new portfolio managers but does not disclose this to clients of the firm
c. An investment advisory firm is purchased by a large broker-dealer and all client contracts are automatically amended to reflect the broker-dealer ownership
d. A client terminates an advisory relationship with an investment adviser halfway through the contract and the advisory firm refunds 50% of all prepaid fees, as called for in the contract.