从刀耕火种到铁犁牛耕的变化最主要反映了()
A.耕作方式的不断改进
B.土地制度的日渐变化
C.人类文明发展阶段的演进
D.小农经济制度的成熟
参考答案:C
甲、乙、丙三数之和是242,乙比丙的2倍少5,甲比丙的3倍多7。甲、乙、丙三数各是多少?
The last time we had great fun was ______ we were visiting the Water Park. [ ]
A. when
B. how
C. where
D. why