在肥沃的土壤中,种子萌发初期(如右图所示)所需要的有机物
A:来自空气
B:来自土壤
C:来自种子
D:部分来自种子,部分来自土壤
His friends asked him ________ up smoking.
x+8,3+10=13,7x+5>3都是方程.