97免费在线观看视频,亚洲综合自拍网,黄色毛片免费观看,热久久综合网,免费看日产一区二区三区 狠狠操av,久久久涩涩涩,在线精品免费视频,人人插天天干,久久91精品国产91久久

單項(xiàng)選擇題

Which of the following statements is NOT considered a characteristic of farming in the late 18th and early 19th centuries?()

A.Use of artificial fertilizer.
B.Introduction of new agricultural machinery.
C.The'Open-field'system.
D.A system of crop rotation.

微信掃碼免費(fèi)搜題