$\int_{0}^{x} f(p) f^{\prime}(p) d p=?$

$\frac{1}{2} f^{2}(x)$

$\frac{1}{2} x^{2}$

$\frac{1}{2}\left[\{f(x)\}^{2}-(f(0)\}^{2}\right]$

$f(x)-f(0)$