用反证法证明命题：若整系数一元二次方程$a{x}^2+bx+c=0(a\ne 0)$有有理数根，那么a,b,c中至少有一个是偶数，下列假设中正确的是               （  ）

    O. Henry was a pen name of an American writer. He wrote short stories. His real name was William Sydney Porter. He was born in North Carolina in 1862. As a young boy he lived an exciting life. He did not go to school for very long, but he tried to teach himself everything he needed to know. When he was about 20 years old, O. Henry went to Texas. There he tried different jobs. He first worked on a newspaper, and then had a job in a bank. When some money was lost from the bank, others believed O. Henry took it. So people sent him to prison﹡. He stayed in prison for three years. There he learned to write short stories. After he got out of prison, he went to New York and went on writing. He wrote mostly about New York and the life of the poor there. People liked his stories, because they always finished with a sudden change at the end, to the reader's surprise.

从分子的角度分析，下列解释错误的是（     ）