请解释下选项B为什么是对的呢？谢谢老师

问题如下：

A market risk team at a hedge fund is developing stress test scenarios to assess the impact of changes in different market variables on the fund’s portfolio of agency-backed MBS. The team wants to identify potential factors that would likely cause the rate of prepayments on the MBS portfolio to increase. Holding all else constant, which of the following would most likely result in increased prepayments in the portfolio?

选项：

A.A decrease in defaults experienced in the mortgage pool

B.A decrease in the average loan-to-value ratio of the mortgage pool

C.An increase in market interest rates

D.An increase in the supply of newly built housing

解释：

B is correct. A decrease in the average loan-to-value ratio is likely to cause curtailments, which are partial prepayments, therefore increasing prepayments.

A is incorrect. A decrease in defaults usually decreases prepayments.

C is incorrect. An increase in market interest rates usually decreases prepayments.

D is incorrect. An increase in the supply of new houses decreases the value of existing houses, thus slowing down refinancing activity for drawing on home equity.