Answer:
The line which contains a metaphor is:
"or press an ear against its hive"
Step-by-step explanation:
Let's be really careful here and resist the temptation of selecting "like a color slide." This line contains a simile, not a metaphor.
A metaphor is a figure of speech that makes a comparison between two different things in order to attribute a quality of one of them to the other. To make such comparison, the metaphor states that "thing A is thing B" - a simile would use a sentence such as "thing A is like thing B."
Having that in mind, we can see that the line "or press an ear against its hive" is the one that contains a metaphor. The speaker is comparing the poem to a hive, as if it is possible to hear sounds inside it just like you would if you pressed your ear against a hive. The speaker wants us to visualize the poem as something else, something full of life and activity.