能解释一下这题的答案么，为何是joint prob？
问题如下图：
选项：
A. 
B. 
C. 
D. 
解释：
When institution hsolexposure to another institution (i.e., purchaseprotection) in a C, it hexchangethe risk of fault on the unrlying asset for whiof the following? fault risk of the counterparty fault risk of a cret exposure intifiethe counterparty Joint risk of fault the counterparty anof the cret exposure intifiethe counterparty Joint risk of fault the counterparty anthe unrlying asset ANSWER: The protection buyer is exposeto the joint risk of fault the counterparty anunrlying cret. If only one faults, there is no cret risk. 您好，大概看了看之前朋友的提问以及解析，但还是觉得有问题。按照这题的问法，说的是一个公司卖C给另一个公司，它exchange的风险有哪些。 卖C保险的公司不是只承受cret exposure的风险吗？还是这道题问的有问题？它逗号后面的\"it\"指代的是C seller啊
When institution hsolexposure to another institution (i.e., purchaseprotection) in a C, it hexchangethe risk of fault on the unrlying asset for whiof the following? fault risk of the counterparty fault risk of a cret exposure intifiethe counterparty Joint risk of fault the counterparty anof the cret exposure intifiethe counterparty Joint risk of fault the counterparty anthe unrlying asset ANSWER: The protection buyer is exposeto the joint risk of fault the counterparty anunrlying cret. If only one faults, there is no cret risk. 您好，这道题C没有懂。为什么C不对呢？
When institution hsolexposure to another institution (i.e., purchaseprotection) in a C, it hexchangethe risk of fault on the unrlying asset for whiof the following? fault risk of the counterparty fault risk of a cret exposure intifiethe counterparty Joint risk of fault the counterparty anof the cret exposure intifiethe counterparty Joint risk of fault the counterparty anthe unrlying asset ANSWER: The protection buyer is exposeto the joint risk of fault the counterparty anunrlying cret. If only one faults, there is no cret risk. 前面问答里提到的C标的资产对手方，是指bonX；C对手方是指insurer么？
为什么不是A，unrlying的fault不是转移给counterparty了吗，需要承担的只是A会违约的counterparty risk？
的unrlying asset违约指的是保险公司的违约吗？
