Sure! Let's identify the silent letters in each word and then use them in a sentence.
thumb - The silent letter is b .
Sentence: The cat's playful paw swatted at my thumb as I reached for the toy.
young - The silent letter is o .
Sentence: The young bird took its first flight from the nest today.
knock - The silent letter is k .
Sentence: I heard a knock on the door in the middle of the night.
know - The silent letter is k .
Sentence: I need to know the answer before the test tomorrow.
Each of these words contains a silent letter, which is a letter written but not pronounced when saying the word. Understanding silent letters is important for both correct spelling and pronunciation.