Cho hàm số \(y=f\left( x \right)\) thỏa mãn \(\int\limits_{0}^{\frac{\pi }{2}}{\sin x.f\left( x \right)\,\text{d}x}=f\left( 0 \right)=1.\) Tính \(I=\int\limits_{0}^{\frac{\pi }{2}}{\cos x.{f}'\left( x \right)\,\text{d}x}.\)
A. \(I=2.\)
B. \(I=-\,1.\)
C. \(I=1.\)
D. \(I=0.\)