6. In the Kingdom of Mathematics, the denominations of banknotes in circulation are 1 yuan, 5 yuan, 10 yuan, 20 yuan, 50 yuan, and 100 yuan. One day, two customers each bought a chocolate bar worth 15 yuan at the same grocery store. One of them paid with two 10-yuan banknotes, while the other paid with a 20-yuan and a 5-yuan banknote. When settling the accounts, the boss only needed to give one 10-yuan banknote from the first person to the second person, and then give the 5-yuan banknote from the second person to the first person. One day, two more customers came to buy chewing gum of the same price, and a similar situation occurred as before, where both paid more than the price. The boss only needed to give part of the first person's payment to the second person, and then give part of the second person's payment to the first person. Therefore, ( ) is a possible price for the chewing gum.
(A) 2 yuan
(B) 6 yuan
(C) 7 yuan
(D) 8 yuan
【Answer】D
【Analysis】Considering the four cases respectively, when the gum costs 8 yuan, one person pays 10 yuan (2 five-yuan notes), and another person pays 13 yuan (1 ten-yuan note, 3 one-yuan notes), the first person's 1 five-yuan note can be given as change to the second person, and the second person's 2 one-yuan notes can be given as change to the first person, thus completing the change. The other cases do not meet the requirements of the problem, so the answer is D.