Cho

Câu hỏi: Cho $f\left(n\right) = {(n^2+n+1)}^2$với ∀n ∈N*. Đặt $u_n = \frac{f\left(1\right). f\left(3\right)...f(2n-1)}{f\left(2\right). f\left(4\right)...f\left(2n\right)}$.

A. n = 23

B. n = 29

C. n = 21

D. n = 33