有个陈述：
Bonds financed by repurchase agreements have less liquidity risk than bonds held as part of a 'buy-and-hold' strategy.
答案说这个陈述是错误的，原因是：
because repurchase agreements expose investors to liquidity risk as the collateral used in the repo is market-to-market periodically.

对这个答案不是很理解，请各位大大帮我解释一下。。谢谢！