C选项解析没看懂，求解释。谢谢~

NO.PZ2018053101000040 问题如下 Whiof the following statements istrue regarng mortgage-backesecurities? A.Insurancompanies prefer the first-losstranche. B.When interest rates rise, prepayments willlikely accelerate. C.When interest rates fall, the low-risk seniortranche will amortize more quickly. Cis correct. When interest rates cline, borrowers are likely to refinancetheir loans a faster pathbefore, resulting in faster amortization ofeaMtranche, inclung the senior tranche, whiis the lowest-risktranche.Ais incorrebecause risk-averse investors, primarily insurancompanies,prefer the lowest-risk tranches, whiare the first to receive interest anrincipal. The junior-most tranche is referreto the first-loss tranche. Itis the highest-risk tranche anis the last to receive interest anprincipalstributions.B is incorrectbecause when interest rates rise, prepayments will likely slow wn,lengthening the ration of most Mtranches. Prepayments will likely increasewhen interest rates cline, because borrowers are likely to refinantheirloans a faster pace. 感觉C很不严谨啊，prepayment risk和Cret risk不能混淆呀，C这个等于把两个东西混在一起了

NO.PZ2018053101000040 问题如下 Whiof the following statements istrue regarng mortgage-backesecurities? A.Insurancompanies prefer the first-losstranche. B.When interest rates rise, prepayments willlikely accelerate. C.When interest rates fall, the low-risk seniortranche will amortize more quickly. Cis correct. When interest rates cline, borrowers are likely to refinancetheir loans a faster pathbefore, resulting in faster amortization ofeaMtranche, inclung the senior tranche, whiis the lowest-risktranche.Ais incorrebecause risk-averse investors, primarily insurancompanies,prefer the lowest-risk tranches, whiare the first to receive interest anrincipal. The junior-most tranche is referreto the first-loss tranche. Itis the highest-risk tranche anis the last to receive interest anprincipalstributions.B is incorrectbecause when interest rates rise, prepayments will likely slow wn,lengthening the ration of most Mtranches. Prepayments will likely increasewhen interest rates cline, because borrowers are likely to refinantheirloans a faster pace. 虽然选对了，但c是啥意思

NO.PZ2018053101000040问题如下 Whiof the following statements istrue regarng mortgage-backesecurities? A.Insurancompanies prefer the first-losstranche.B.When interest rates rise, prepayments willlikely accelerate.C.When interest rates fall, the low-risk seniortranche will amortize more quickly. Cis correct. When interest rates cline, borrowers are likely to refinancetheir loans a faster pathbefore, resulting in faster amortization ofeaMtranche, inclung the senior tranche, whiis the lowest-risktranche.Ais incorrebecause risk-averse investors, primarily insurancompanies,prefer the lowest-risk tranches, whiare the first to receive interest anrincipal. The junior-most tranche is referreto the first-loss tranche. Itis the highest-risk tranche anis the last to receive interest anprincipalstributions.B is incorrectbecause when interest rates rise, prepayments will likely slow wn,lengthening the ration of most Mtranches. Prepayments will likely increasewhen interest rates cline, because borrowers are likely to refinantheirloans a faster pace. 是哪一层呢，有什么特点

NO.PZ2018053101000040问题如下 Whiof the following statements istrue regarng mortgage-backesecurities? A.Insurancompanies prefer the first-losstranche.B.When interest rates rise, prepayments willlikely accelerate.C.When interest rates fall, the low-risk seniortranche will amortize more quickly. Cis correct. When interest rates cline, borrowers are likely to refinancetheir loans a faster pathbefore, resulting in faster amortization ofeaMtranche, inclung the senior tranche, whiis the lowest-risktranche.Ais incorrebecause risk-averse investors, primarily insurancompanies,prefer the lowest-risk tranches, whiare the first to receive interest anrincipal. The junior-most tranche is referreto the first-loss tranche. Itis the highest-risk tranche anis the last to receive interest anprincipalstributions.B is incorrectbecause when interest rates rise, prepayments will likely slow wn,lengthening the ration of most Mtranches. Prepayments will likely increasewhen interest rates cline, because borrowers are likely to refinantheirloans a faster pace. 保险公司不是在投资人出现损失的时候会承担赔付吗？

NO.PZ2018053101000040问题如下 Whiof the following statements istrue regarng mortgage-backesecurities? A.Insurancompanies prefer the first-losstranche.B.When interest rates rise, prepayments willlikely accelerate.C.When interest rates fall, the low-risk seniortranche will amortize more quickly. Cis correct. When interest rates cline, borrowers are likely to refinancetheir loans a faster pathbefore, resulting in faster amortization ofeaMtranche, inclung the senior tranche, whiis the lowest-risktranche.Ais incorrebecause risk-averse investors, primarily insurancompanies,prefer the lowest-risk tranches, whiare the first to receive interest anrincipal. The junior-most tranche is referreto the first-loss tranche. Itis the highest-risk tranche anis the last to receive interest anprincipalstributions.B is incorrectbecause when interest rates rise, prepayments will likely slow wn,lengthening the ration of most Mtranches. Prepayments will likely increasewhen interest rates cline, because borrowers are likely to refinantheirloans a faster pace. 如果是low risk senior tranche , repayment risk 也是最低吗？如果是，那应该是high risk subornate tranche先收到提前还款啊？