6. Let $f ( x ) = x - [ x ]$, for every real number $x$, where $[ x ]$ is the integral part of $x$. Then $\int 1 - 1 f ( x ) d x$ is : (A) 1 (B) 2 (C) 0 (D) $1 / 2$
6. Let $f ( x ) = x - [ x ]$, for every real number $x$, where $[ x ]$ is the integral part of $x$. Then $\int 1 - 1 f ( x ) d x$ is :\\
(A) 1\\
(B) 2\\
(C) 0\\
(D) $1 / 2$\\