I think that the answer is A, but the answer B is also correct in some situation because a cash flow matched portfolio is easier to construct than an immunized portfolio (Duration matching) depending on the situation.
There is no direct description for this in the textbook.
Thank you in advance.
Compared to an immunized portfolio, a cash flow matched portfolio:
A. Usually is more difficult to construct, but is easier to maintain after it has been constructed.
B. Usually is more expensive to maintain after it has been constructed.
C. Can be easily changed after it has been constructed,