Treasury securities are the most liquid of the investments mentioned.
The repurchase market is short term in nature and the collateral is marked-to-market daily. Thus, the need to quickly convert securities to cash (and at approximately market value) is very important. Emerging markets are usually less liquid than established markets, one reason being the small trading volumes. Even if an investor intends to hold the security to maturity, liquidity risk impacts portfolios when marking to market and through changes in investor tastes and preferences over time. For example, liquidity is important to institutional investors that must determine market values for net asset values (NAVs).