26. Let $f ( x ) = \int ^ { x } { } _ { 1 } \sqrt { } \left( 2 - t ^ { 2 } \right)$ The real roots of the equation $x ^ { 2 } - f ^ { \prime } ( x ) = 0$ are\\ (A) $\quad \pm 1$\\ (B) $\pm 1 / \sqrt { } 2$\\ (C) $\quad \pm 1 / 2$\\ (D) 0 and 1\\