dollar roll 和 repo

问题如下：

Explain how a dollar roll works and why it is different from a repo as a way of using securities that are owned to borrow money.

选项：

A.

A dollar roll involves selling a pool of securities in one month and buying a similar pool back the next month, without requiring the same pool to be returned or explicit interest added to the price, while a repo involves selling and repurchasing the exact same securities with interest added to the repurchase price.

B.

A dollar roll involves selling a pool of securities in one month and buying the exact same pool back the next month, with interest added to the repurchase price, while a repo involves selling and repurchasing similar securities without requiring the same pool to be returned.

C.

A dollar roll involves selling a pool of securities in one month and buying a similar pool back the next month, with interest added to the repurchase price, while a repo involves selling and repurchasing the exact same securities without requiring interest to be added.

D.

A dollar roll involves selling a pool of securities in one month and buying a similar pool back the next month, with interest added to the repurchase price, while a repo involves selling and repurchasing similar securities without requiring the same pool to be returned.

解释：

A dollar roll involves raising funds by selling a pool in one month and buying a similar pool back the following month. Properties such as coupon, principal, and maturity are specified but the party with a short position chooses the actual pool that will be delivered. This means that the pool that is received during the second month may be different from the one sold during the first month. This is one difference between a dollar roll and a repo. The other difference is that interest does not have to be added to the price paid in the second month because the trader who sells and then buys loses one month of MBS income,while the trader on the other side gains one month of MBS income.

解释一下dollar roll是怎么运作的？为什么在借款的时候和repo不一样？

第一，dollar roll是一个滚动的资金池，通过出售资产池并在下一个月购买一个类似的资产池来筹集资金。会指定coupon大小，本金以及到期日等属性。但是repo是要求回购相同的资产。

第二，dollar roll的利息不用加到价格里面，而repo的利息是通过买卖价差计算出来的。