A:Fe2O3
B:C
C:Fe
D:CO2
—Excuse me! You can't take photos here.Look at the sign. It says “NO PHOTOS”.
— Sorry,I _________ see it and I _______ do it.
已知关于x的方程k-1x2-2kx+k+1=0(k为实数),则其根的情况是
如图是心脏、血管的示意图,“→”表示血流方向,下列表述正确的是( )