NO.PZ2019052001000031
问题如下：
How is the loss distribution approach (LDA) usually used for risk measurement?
选项：
A. Model frequency of loss and severity of loss separately.
B. Model severity of loss but not frequency of loss.
C. Model frequency of loss but not severity of loss.
D. Model frequency of loss and severity of loss in a single bivariate distribution.
解释：
A is correct.
考点：loss distribution approach（LDA）
解析： LDA分别对损失的频率和损失的严重程度进行建模。 对于损失频率，LDA模型使用泊松分布，负二项分布或二项分布。 损失严重程度通常使用对数正态分布建模。
请问A和D有什么不同
