What actually is the part labelled as [1, [...]?

What actually is the part labelled as [1, […] ?

t = [1]
s = [t]
t.append(s)
print(s)

output : [[1, […]]]

I answerede the question as 1, but still wrong.

Is there other alternative ? Thank you.

Link?
Is this an exam question? If so, we cannot help with exams.