选择用哪个折现率不是属于model范畴么，跟用pbo还是abo是一个道理吧

问题如下：

The risk that Silver describes to Shrewsbury in hedging the liabilities is most likely:

选项：

A.model risk.

B.spread risk.

C.liquidity risk.

解释：

B is correct. Silver is referring to spread risk in his discussion with Shrewsbury regarding risks in hedging DB plan liabilities. The liabilities are estimated—that is, calculation of the PBO—using high-quality corporate bonds. The typically wider spreads of lower-quality bonds may underperform the spreads of higher-quality bonds in a market sell-off. Conversely, hedging the liabilities with swaps may not provide enough of a spread risk hedge relative to using corporate bonds such that if spreads tighten, high-quality corporate bonds (used to discount liabilities) may outperform swaps. Model risk refers to making incorrect assumptions regarding future liabilities or approximations being inaccurate. Liquidity risk is associated with exhausting available collateral funds to meet margin calls on derivative positions or to pay benefits.

A is incorrect because model risk refers to making incorrect assumptions regarding future liabilities or approximations being inaccurate.

C is incorrect because liquidity risk is associated with exhausting available collateral funds to meet margin calls on derivative positions or to pay benefits.