Answer: Love in my heart was a fresh tide flowing.
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 poem by Sara Teasdale we can see an example of a metaphor in the line "Love in my heart was a fresh tide flowing" this is a comparison between love and a tide flowing. Notice that the comparison is direct (it doesn't use the words "like" or "as).