What impelled the boy to take so much trouble to spare the feelings of a stranger？

What impelled the boy to take so much trouble to spare the feelings of a stranger？
A、Why did the boy trouble himself to save stranger？
B、Why did the boy try so hard to make friends with a stranger？
C、Why did the boy try his best to build up the confidence of a stranger？
D、Why did the boy make such great efforts in order not to embarrass a stranger？
正确答案：D