Cho

Câu hỏi: Cho $f\left(n\right)={\left(n^2+n+1\right)}^2,\forall n\in \mathbb{N}*.$ Đặt $u_n=\frac{f\left(1\right).f\left(3\right)\mathrm{...}f\left(2n-1\right)}{f\left(2\right).f\left(4\right)\mathrm{...}f\left(2n\right)}.$ 

A. n = 23

B. n = 29

C. n = 21

D. n = 33