Read the excerpt from "You are Old, Father William," by Lewis Carroll. Identify the pair of lines that expresses a humorous tone. "You are old, Father William," the young man said,

"And your hair has become very white;

And yet you incessantly stand on your head—

Do you think, at your age, it is right?"

"In my youth," Father William replied to his son,

"I feared it might injure the brain;

But, now that I'm perfectly sure I have none,

Why I do it again and again."

I believe the pair of lines that expresses a humorous tone is:

"But, now that I'm perfectly sure I have none,  

Why I do it again and again."

Explanation:

The pair of lines above is dictating the humorous tone of the poem "You are Old, Father William". It ends the interaction between father William and his son in a comical, surprising way. The father is obviously older than his son, which leads us to expect him to be wiser. Still, he claims to have no brain. Perhaps he means he has lost his mind, which would explain why he stands on his head at such an age. It's as if he is aging backwards - his body growing older, but his mind getting younger.

we need the passage first