Question

欅48

出来れば早急に教えて欲しいのですが。

Louise：Hi. This is Louise calling.
I’ve just finished the report
that’s due tomorrow morning for Professor Green....
Peter ：That report’s due tomorrow morning?
Oh, no! I’m in trouble!
It’s already 11:30 p.m.
and I haven’t even started writing it.
I’ll have to work all night.
If I can turn it in by 9 a.m.,
it’ll be by the skin of my teeth.
In this dialogue,
by the skin of my teeth means ()

① barely in time ② hard to chew
③ morally right ④ quite late

この問題の答えと解答の根拠を教えて欲しいです。