Give me a hand?

[Murzik]

Test No. incompl/inter-25 "Wrapped round her finger", question 8

Could you please give me a ......... I'm afraid I can't handle it by myself.

(a) tooth
(b) foot
(c) hand
(d) finger

Test No. incompl/inter-25 "Wrapped round her finger", answer 8

Could you please give me a hand I'm afraid I can't handle it by myself.

Correct answer: (c) hand

Your answer was: incorrect
Could you please give me a finger I'm afraid I can't handle it by myself.
_________________________

why the word finger doesn't fit in here?
thanks

[Torsten]

Because it's a set phrase (an idiom).

TOEIC listening, talks: A radio commercial for a herbal sleeping pill