Nếu 

Câu hỏi: Nếu ${\int }_0^{\mathrm{\pi }}f\left(x\right)\sin xdx=20, {\int }_0^{\mathrm{\pi }}xf\text{'}\left(x\right)\sin xdx=5$ thì ${\int }_0^{{\mathrm{\pi }}^2}f\left(\sqrt{x}\right)\cos \left(\sqrt{x}\right)dx$ bằng:

A. -30

B. -50

C. 15

D. 25