In recent years, large dealer banks financed significant fractions of their assets using short-term, often overnight repurchase (repo) agreements in which creditors held bank securities as collateral against default losses. The table below shows the quarter-end financing of four broker-dealer banks. All values are in USD billions:

| | Bank A | Bank B | Bank C | Bank D |

|--------------------------|--------|--------|--------|--------|

| Financial instruments owned | 823 | 629 | 723 | 382 |

| Pledged as collateral | 272 | 289 | 380 | 155 |

In the event that repo creditors become nervous about a bank's solvency, which bank is least vulnerable to a liquidity crisis?