Assuming that you can lend at the risk-free rate but cannot borrow at that rate, your choice of optimal portfolio is. Unaffected at all levels of...

Assuming that you can lend at the risk-free rate but cannot borrow at that rate, your choice of optimal portfolio is..

a. Unaffected at all levels of risk.

b. Restricted at low levels of risk but unaffected at high levels of risk.

c. Unaffected at low levels of risk but restricted at high levels of risk.

d. Affected at all levels of risk.

e. None of the above.