Chọn câu đúng

* Hướng dẫn giải

Ta có

$\frac{31}{2}.\frac{32}{2}.\frac{33}{2}\mathrm{...}\frac{60}{2}=\frac{\mathrm{31.32.33...60}}{\mathrm{2.2.2....2}}$

$=\frac{\left(\mathrm{31.32.33...60}\right)\left(\mathrm{1.2.3...30}\right)}{2^{30}\left(\mathrm{1.2.3...30}\right)}$

$=\frac{\mathrm{1.2.3.4.5...60}}{\left(1.2\right).\left(2.2\right).\left(3.2\right).\left(4.2\right)\mathrm{...}\left(30.2\right)}$

$=\frac{\left(\mathrm{2.4.6...60}\right)\left(\mathrm{1.3.5.7...59}\right)}{\mathrm{2.4.6...60}}$

= 1.3.5…59

Đáp án cần chọn là: B