以下不属于中国古代精耕细作农业突出成就的是
A：开发圩田
B：间作、套种和复种
C：较早使用耒耜
D：科学育种与掌握农时
选词填空。
A. This is Mary. She's nine. She's tall. She's thin.
B. This is Danny. He's six. He's short. He's fat.
C. This is Eddie. He's nine. He's short. He's thin.
骨含有比例适当的____和____ ，使骨具有一定的硬度和弹性，硬而不脆．
