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

Sentence: 'the cargo train is headed to the next destination'. Replace the letter 'h' with 'x' in the sentence.
txe cargo train is xeaded to txe next destination

Sentence: 'a police officer on a horse is riding down the street'. Replace the letter 'h' with 'a' in the sentence.
a police officer on a aorse is riding down tae street

Sentence: 'a couple of cats on the ground in a room'. Replace the letter 'a' with 'p' in the sentence.
p couple of cpts on the ground in p room