A:C2H4
B:C3H6
C:C4H8
D:C5H12
Look! is a pen. And are pencils.
有“绿色水库”之称的生态系统是( )。
=21.32-6.32-8.3
=15-8.3
=6.7
设复数z满足4z+2z-=33+i,ω=sinθ-icosθ,(θ∈R).求z的值和|z-ω|的取值范围.
读“某地气温年变化曲线图”(如图所示),据此判断该地位于( )