Which one? · initial only
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听一听，是哪一个？
Both answers are tone 4 and end the same way — only the first sound changes.
You picked shì — the curled one. That is 是, the word you say next.
A
sh
Tip curled back
shì
是
am, is
B
s
Tip flat, at the teeth
sì
四
four
One initial apart — and you can hear it.
Why do they sound alike?