题干
—Thank you for carrying me to hospital, young man! It's kind of you.
—_____________. Helping others makes me happy.
A： Yes, please
B：No, thank you
C：You are welcome
D：No, you don’t have to
答案(点此获取答案解析）
C
，且
与
垂直，
垂直，
与
的夹角的余弦值为（ ）