It was Friday, the day of the field trip on which Miss Joan would take her class to pick a

Miss Joan enjoyed picking apples with her students. She smiled as she led her students to the bus that would take them to the Greenly Apple Orchard (果园) .

The bus ride was bumpy and the kids were a little noisy, but still Miss Joan was smiling.

The bus stopped in front of the Greenly Apple Orchard and the class got off quickly and quietly. Miss Joan made sure everyone was there. "What a glorious, sunny, apple picking day," Miss Joan announced with her grandest smile.

Mr. Greenly was there to greet them. "Let's see, there are eighteen children and two adults at three dollars each. That will be sixty dollars, please."

Miss Joan held up the brochure in her hand. "It says that the price is two dollars each," she pointed out. "That's what I collected from everyone."

"We've had to raise the price," Mr. Greenly stated.

"You sent me this brochure after we made our reservation," Miss Joan complained, "and it says two dollars!"

"Miss Joan, if you look at the bottom of this brochure," Mr. Greenly said, "you'll notice very important statement."

Sure enough, in very tiny letters, it said, "Prices are subject to change without notice."

Miss Joan was determined to keep her good mood. She took a twenty dollars bill out of her own purse and handed it to Mr. Greenly with the forty dollars she had in an envelope. "Now children, do you all have your baskets？" Miss Joan called out. "Remember, each of you can pick as many apples as possible."

Mr. Greenly said, "You can't pick as many apples as possible."

"I beg your pardon？ Miss Joan was not smiling now. "The brochure says, 'ALL YOU CAN PICK'!"

Mr. Greenly pointed to the tiniest letters Miss Joan had ever almost seen. It also says, "Terms and conditions of group reservations are subject to change without notice."

Miss Joan's good mood was now history. She didn't want to set a bad example for her students, so she said in a calm and quiet voice, "We're going home, give me our money back, please."

How many dollars did Miss Joan hand to Mr. Greenly？

A．20.

B．40.

C．60.

D．18.