Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: It could have been everything , and it could have been nothing . I think I was past caring . I walked , because there was nothing else for me to do . My chest still felt tight , like a coil wound .

Question: What may be a reason their chest was tight ?
None of the above choices .
Stress or anxiety.