A:若同位角相等,则两直线平行
B:若x,y全为0,则x=0且y=0
C:若方程x2+2x+m=0有实根,则m≥0
D:若x2﹣3x+2>0,则x2﹣3x>0
黄土高原地区最严重的生态环境问题是( )
某哺乳动物神经细胞内外的K+和Na+浓度见下表。下列属于主动转运的是( )
—This box is ________ heavy for me to carry. Can you help me?
—Certainly.