问题如下：
Which of the following forms of infrastructure investments is the most liquid?
选项：
A. An unlisted infrastructure mutual fund
B. A direct investment in a greenfield project
C. An exchange-traded master limited partnership (MLP)
解释：
C is correct.
A publicly traded infrastructure security, such as an exchange-traded MLP, provides the benefit of liquidity.
关于不同投资方式的流动性，可以有个简单的规律：间接投资的流动性比直接投资的流动性好，在间接投资中，公开市场交易的产品流动性要比非公开市场交易的产品流动性好。MLP对应的就是公开交易的间接型投资产品，因此流动性最好。
ABC分别翻译成中文是什么？