用數(shù)學(xué)歸納法證明“(n+1)(n+2)…(n+n)=2ⁿ·1·3·…·(2n-1)(n∈N)時(shí)”,從“n=k到n=k+1”,左邊需增乘的代數(shù)式是(　　)

A.2k+1                  B.              C.2(2k+1)             D.

利用數(shù)學(xué)歸納法證明（n+1）(n+2)…(n+n)=2n·1·3·…·（2n-1）時(shí)，由k到k+1左邊應(yīng)添加的因式是（    ）

A.2k+1                                                    B.

C.                                 D.

用數(shù)學(xué)歸納法證明“(n+1)(n+2)·…·(n+n)=2ⁿ·1·3·…·(2n-1)”,從“k到k+1”左端需增乘的代數(shù)式為(    )

A.2k+1                           B.2(2k+1)

C.                         D.

用數(shù)學(xué)歸納法證明“(n+1)(n+2)…(n+n)=2ⁿ·1·3·…·(2n-1)(n∈N)時(shí)”,從“n=k到n=k+1”,左邊需增乘的代數(shù)式是(　　)

A.2k+1                  B.              C.2(2k+1)             D.

用數(shù)學(xué)歸納法證明(n+1)(n+2)(n+3)…(n+n)=2ⁿ×1×3×…×(2n-1)時(shí)，從“k到k+1”左邊需增乘的代數(shù)式是(    )

A.2k+1          B.             C.2(2k+1)              D.