Amanda talks with several different brokers at a social gathering. She hears the following advice from brokers A, B, and C. Which broker, if any, gave her incorrect advice? a. Broker A: "There are risks in holding stocks, even in a highly diversified portfolio." b. They all gave her correct advice. c. Broker B: "Portfolios with smaller standard deviations have lower risk." d. Broker C: "Stocks with greater risks offer lower average returns