Correct Answer: ni

Solution : Given:
1. ear eyes nose chin cheeks ⇒ si ei ki ri ni
2. nose legs hands fingers ⇒ gi fi di ei
3. eyes ear hands ⇒ ri si di
4. legs cheeks eyes ⇒ ki gi si

By comparing the coded sentences, we find that –
In sentences 1, 3, and 4, eyes and si are common.
In sentences 1 and 3, ear and ri are common.
In sentences 1 and 2, nose and ei are common.
In sentences 1 and 4, cheeks and ki are common.
In sentences 2 and 3, hands and di are common.
In sentences 2 and 4, legs and gi are common.
​​​The remaining words and code in sentence 1 are chin and ni ; in sentence 2 are fingers and di .
So, eyes ⇒ si; ear ⇒ ri; nose ⇒ ei; cheeks ⇒ ki; hands ⇒ di; legs ⇒ gi; chin ⇒ ni; fingers ⇒ di

So, the chin is coded as ni . Hence, the first option is correct.