MLP的全称和具体内涵是什么啊？

问题如下：

An investor is considering invest in infrastructure, but he is worry about liquid risk. Which investment is suitable for him?

选项：

A.An unlisted infrastructure mutual fund B.A direct investment in a greenfield project C.An exchange-traded MLP

解释：

公开交易的基建证券，如公开交易的MLP，提供了很好的流动性。