Which one of the following portfolios cannot lie on the efficient frontier as described by markowitz?
portfolio expected return standard deviation
w 9 % 21 %
x 5 % 7 %
y 15 % 36 %
z 12 % 15 %

(a) only portfolio w cannot lie on the efficient frontier.
(b) cannot be determined from the information given.
(c) only portfolio y cannot lie on the efficient frontier.
(d) only portfolio z cannot lie on the efficient frontier.
(e) only portfolio x cannot lie on the efficient frontier.