A、$15. B、$12. C、21 D、9 D题目询问男士买玫瑰花费多少钱。由女士的话可知玫瑰花的价格是“…a half for eachred rose”，男士说“I’d like…half a dozen redroses．”因此正确答案应该是选项D

M: How much are the carnations and the roses?
W: One dollar for each carnation and(9)one and a half for each red rose.
M:(9)Then I’d like a dozen red carnations and half a dozen red roses.
W: I bet it’s for your mother,(8)as it’s Mother’s Day today.
M: Well, not completely true.(8)It happens to be her birthday.
W: Oh, really? I guess she must be very happy to receive these beautiful carnations from you.
M: Yeah, she will. She really likes flowers. So I buy her some every year. I’d just wish they would stay fresh longer than they do.
W:(10)Put a little sugar and vitamin C in the water. They’ll stay fresh for days.
M: Really? I’ll tell my mother. And thanks for your suggestion.
W: That’s all right. Happy birthday to your mother!
Questions 8 to 10 are based on the conversation you’ve just heard.
8. What day is it today?
9. How much does the man spend on red roses?
10. What does the woman suggest the man put in the water?