A major setback of the Arbitrage Pricing Model $($APT$)$ is that:

a$)$ The factors are not specified

b$)$ The number of factors is not specified

c$)$ Factors are often correlated with one another

d$)$ All of the above

The set of portfolios that has the maximum return for a given level of risk or the minimum risk for a given level of return, is known as the:

a$)SML$

b$)CML$

c$)$ Efficient Frontier

d$)$ Market proxy

The optimal portfolio for a given investor lies at the point of tangency between the and the individual investor's

a$)$ Efficient frontier; utility curve

b$)$ Utility curve; efficient frontier

c$)$ SML; utility curve

d$)$ Utility curve; SML