A:Mg2+吸收
B:O2扩散
C:CO2的固定
D:DNA复制
关于x、y的二元一次方程组3x+y=1+3ax+3y=1-a的解满足不等式x+y>0,则a的取值范围是( )
“黄金有价、玉无价”,某一种玉石的主要成份是NaAlSi2O6,下列说法正确的是( )
— Wonderful! I think it is ______ a meaningful TV show that ______ many people like watching it.