While people in other countries in the world were trying to catch wild animals and birds and were still collecting seeds and nuts, farmers in China were developing the science of agriculture.
A.当世界上其他国家还在捕猎飞禽走兽、采集种子坚果的时候，中国的农民就已经开始发展农业科技了。 B.当世界上其他国家还在捕猎飞禽走兽、采集种子坚果的时候，中国的农民就已经在从事农业科技研究了。 C.当世界上其他国家的在捕猎飞禽走兽、采集种子坚果的时候，中国的农民开始了农业科技的研究了。 D.当世界上其他国家的人们还在捕猎飞禽走兽、采集种子坚果的时候，农业科技就已经被中国的农民开始研究了。正确答案B
