There are many people in the bus and there are no empty(空的) seats. When a young man gets on, an old man near him wants to stand up, but the young man push(推) him back to his seat.

“ Thank you,” he said,”but please don’t do that, I can stand.”

“But, young man……”

“I ask you to keep the seats,” the young man doesn’t let the old finish his words.

But the old man again wants to get up. He says,” Young man, please let me……”

“No，no”says the young man, and then he pushes the old back into his seat again.

At last, the old man gets up from his seat. He says to the young man, “You make me three times away from my home. I want ……”

(   )6. The young man has to stand in the bus because _____.

A. there are a lot of people in the bus  B. an old man is in his seat

C. he likes to do so                D. there is no free seats in the bus