从A—J选项中选出能填入空白处的最佳选项补全对话。（选项中有两项是多余的）
Salesperson：____ We're planning to have a big sale
next week.
Customer：____
Salesperson： Meat products will be on sale for 20% off.
Customer： What about vegetables?
Salesperson：____
Customer： Sounds great! ____
Salesperson： Seafood products will be on sale for 30% off.
Customer： ____
Salesperson： Of course! ____ I'm sure you will be satisfied.
Customer： OK. ____
Salesperson： About 9：00 o'clock. You'd better come here earlier. There must be lots of people coming here
that day.
Customer：____
是定义在
的可导函数，对
，都有
，且
，则
