In this task, you need to replace a letter in the sentence with another given letter.

Sentence: 'a zebra standing by a pile of large rocks'. Replace the letter 'i' with 'x' in the sentence.
a zebra standxng by a pxle of large rocks

Sentence: 'a tennis player throwing a ball at the ground'. Replace the letter 'r' with 'f' in the sentence.
a tennis playef thfowing a ball at the gfound

Sentence: 'a man on a motorcycle is waiting at a stoplight'. Replace the letter 't' with 'y' in the sentence.

a man on a moyorcycle is waiying ay a syoplighy