Answer: A) life.
Explanation: a metaphor is a figure of speech that consists in making a direct comparison between elements that aren't obviously related, in order to create an image in the reader's mind. In the given speech, we can see an example of a metaphor that compares a river to life, it is shown in phrases like "we can no more see to the bottom of the next few hours, than we can see to the bottom of this river."