下列哪项不属于北伐战争的主要对象( )
A:张作霖
B:吴佩孚
C:孙传芳
D:袁世凯
若不等式x2+ax+1≥0对任意x∈(0,12成立,则a的最小值为( )
How to keep healthy
As a middle school student, I think it is really important to keep healthy.