Cash flow matching CFA online question

CFA Level III Portfolio Management
#1

Exhibit 2: Selected Plan Portfolio Statistics
||Lawson|Wharton|
|Market value of assets|USD15,498,000|USD8,351,000|
|Duration of assets|7.79|7.82|
|Duration of liabilities|7.78|10.01|
|Semiannual portfolio dispersion|46.07|147.22|
|Accumulated benefit obligation|USD14,389,000|USD7,470,000|
|Portfolio cash flow yield|4.47%|4.51%|

Which of the following three strategies is least likely appropriate for the plans in Exhibit 2?

  1. Duration matching
  2. Cash flow matching
  3. Contingent immunization

Solution: B is correct.
Can someone pls expain why? Thank you!

#2

Where is this question, curriculum or somewhere else?

Both portfolios looks are sufficiently funded. Lawson has its duration pretty well matched but Wharton isn’t, in which liability has a much longer duration than assets, also with much higher dispersion and convexity. I am assuming the premise for cashflow matching is that one should be able to be fairly certainly of the cashflows for the liabilities right?

Is there more context to help clarify the certainty of those cashflows? if not, maybe that is the reason why cashflow matching might be inappropriate.