TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a couple of brown bears walking across a lush green field'. Replace the letter 'w' with 'o' in the sentence.

SOLUTION: a couple of broon bears oalking across a lush green field

PROBLEM: Sentence: 'a young baseball player throws the ball as others watch'. Replace the letter 'a' with 'n' in the sentence.

SOLUTION: n young bnsebnll plnyer throws the bnll ns others wntch

PROBLEM: Sentence: 'a group of people on the pavement next to a monument'. Replace the letter 't' with 'b' in the sentence.

SOLUTION:
a group of people on bhe pavemenb nexb bo a monumenb