Biểu thức 2023/ 2022-2021 . 2021/2023 bằng

Đáp án đúng là: B

Ta có $\frac{2023!}{2022!-2021!}\cdot \frac{2021}{2023}=\frac{2023!}{2021!.\left(2022-1\right)}\cdot \frac{2021}{2023}$

$=\frac{2023!}{2021!.2021}\cdot \frac{2021}{2023}=\frac{2023.2022}{2021}\cdot \frac{2021}{2023}=2022.$