根据短文内容,判断正误。
John went to visit his 90-year-old grandfather in the countryside. He was so old and sometimes he did silly(傻的) things.
The next morning, John's grandfather made him breakfast. However, John saw something on his plate(盘子), and asked his grandfather, "Are these plates clean?" " If they are good enough(足够) for Mr. David, they are good enough for you. Just finish your meal!" his grandfather answered. Mr. David must be an important person (人), John thought.
At lunch, John found that the plates had something dirty(脏的) on them and asked, "Are you sure these plates are clean?" "I told you Mr. David also used them. Now I don't want to hear(听到) any more about it!" the old man said.
That afternoon, when John was going home, his grandfather's dog started to bark(吠), not letting him pass. "Be quiet, Mr. David!" the old man shouted (大喊).