一个物体由多个完全相同的小正方体组成,它的三视图如图所示,那么组成这个物体的小正方体的个数为()
A:2个
B:3个
C:5个
D:10个
_______ you have visited the Great Wall, you can't imagine how great it is.
用数学归纳法证明“(n+1)(n+2)•…•(n+n)=2n•1•3•…•(2n﹣1)”,当“n从k到k+1”左端需增乘的代数式为( )