They can't sell them to get money so the Fed is saying fine we'll just take those and we'll give you Treasury bills which are completely everyone trusts them.

他们不能够卖掉资产来获取金钱,所以美联储说，好吧，我们拿走你的资产,给你完整的国库券,每个人都相信他们。

耶鲁公开课 - 金融市场课程节选