This is called an alliteration.
An example of alliteration would be V's famous speech in V for Vendetta where he uses the letter V at the beginning of each word in an entire speech.
She doesn't recognize him
I had to confer with the principle about leaving school grounds in the middle of the day.
Answer:
The children promised <em><u>to </u></em><em><u>be</u></em> back by mine.
