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

Sentence: 'a family opens gifts in a room with their dog, while sitting on couches'. Replace the letter 's' with 'l' in the sentence.
a family openl giftl in a room with their dog, while litting on couchel

Sentence: 'a book shelf full of books and nick nacks '. Replace the letter 'o' with 'm' in the sentence.
a bmmk shelf full mf bmmks and nick nacks 

Sentence: 'a white and blue airplane sits on a lot next to a passenger loading dock'. Replace the letter 'a' with 'd' in the sentence.

d white dnd blue dirpldne sits on d lot next to d pdssenger lodding dock