Determine the inflection points and intervals of concavity for the function $y=3x-\sin x$, where $-\pi \le x\le \pi$.

• A. Inflection point: $x=0$Concave down on $(-\pi ,0)$Concave up on $(0,\pi )$
• B. Inflection point: $x=0$ Concave down on $(0,\pi )$Concave up on $(-\pi ,0)$
• C. Inflection point: $x=\pi$Concave down on $(0,\pi )$Concave up on $(-\pi ,0)$
• D. Inflection point: $x=-\pi$ Concave down on $(-\pi ,0)$Concave up on $(0,\pi )$