Correct Answer: mel

Solution : Given:
1. trek to the mountain ⇒ tes mel fern lor
2. the mountain is high ⇒ lor max fern ani
3. high to the sky ⇒ tes ani sav fern

By comparing all the three coded sentences, we find that –
In sentences 1, 2, and 3, the and fern are common.
In sentences 1 and 2, mountain and lor common.
In sentences 1 and 3, to and tes are common.
In sentences 2 and 3, high and ani are common.
The remaining words and code in sentence 1 are trek and mel ; in sentence 2 are is and ani ; in sentence 3 are sky and sav .
Finally, the ⇒ fern; mountain ⇒ lor; to ⇒ tes; high ⇒ ani; trek ⇒ mel; is ⇒ ani; sky ⇒ sav

So, trek will be coded as mel. Hence, the third option is correct.