Q:Read the article and select the best answer. Article: Warm water freezes more quickly than cold water. Sir Francis Bacon said that almost four hundred years ago. But few people believed him until 1970. In that year a Canadian scientist George Kill proved the English professor was right. Dr Kill filled an open oil pail with cold water. He filled another with warm water. He put both in the same low temperature. The warm water froze first. The lack of covers on the pails is the secret. Some of the warm water changed into vapor. This meant that less of the warm water was left to be frozen. And so the warm water froze faster than the cold water even though it had a greater temperature drop to make. Question: What Sir Francis Bacon said was right, but people didn't believe him until _ . Options: A: late in the 19th century B: early in the 20th century C: three years ago D: late in the 20th century
A:
D