Answer:
6. Metaphor
7. The figurative language used here is metaphor. In the poem, the world is being compared to a airtight cattle wagon to describe the feelings or emotions of people (Jews) being locked up in ghettos during the world war 2 with no air making many suffocate. It describes their despair & anxiety.
There's no use of 'like' or 'as', hence it's not a similie. There's no imaginative description as well nor does it get the reader to perceive the line from his/her imagination, so it's not an example of imagery as well. It's definitely not a personified line as no object is given a human trait here.
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