根据短文内容选择正确答案。

      A well-known old man was being interviewed and was asked if it was correct that he had just celebrated his ninety-ninth birthday.

     “That's right.” said the old man. “Ninety-nine years old, and I haven't an enemy in the world. They're all dead.”

  “Well, sir,” said the interviewer, “I hope very much to have the honour of interviewing you on your hundredth birthday.”

     The old man looked at the young man closely, and said, “I can't see why you shouldn't look fit and healthy to me!”

孟德尔遗传规律不适用于原核生物，原因是(   )

类推是学习化学的一种重要方法。下列类推正确的是 （   ）