TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'two zebras are snuggling at the zoo in their display area'. Replace the letter 'e' with 'z' in the sentence.

SOLUTION: two zzbras arz snuggling at thz zoo in thzir display arza

PROBLEM: Sentence: 'a polar bear relaxing in a man-made pool'. Replace the letter 'r' with 'x' in the sentence.

SOLUTION: a polax beax xelaxing in a man-made pool

PROBLEM: Sentence: 'a group of red trains parked in a train lot next to a mountain'. Replace the letter 'o' with 'e' in the sentence.

SOLUTION:
a greup ef red trains parked in a train let next te a meuntain