Question

the following questions refer to \i have been to the mountaintop\ by martin luther king jr. (pp. 211 - 220).
in paragraph 20, the phrase \we knew water\ most closely means that king and his audience
are familiar with waters properties.
have been full of unquenchable fire.
are ordained to prevail in the current struggle.
have overcome a surprisingly strong obstacle.
have been baptized in water rituals.

Explanation:

In the context of the speech, "we knew water" is a metaphor. It refers to having overcome a difficult situation (like water being an obstacle that was overcome). The other options either take the phrase too literally (like being familiar with water's properties or water rituals) or don't fit the metaphorical context as well as overcoming an obstacle.

Answer:

have overcome a surprisingly strong obstacle.