If f(x)=cos(x)−1+2x2, then
<spanclass=′latex−bold′>(A)</span>f(x) is an increasing function on the real line<spanclass=′latex−bold′>(B)</span>f(x) is a decreasing function on the real line<spanclass=′latex−bold′>(C)</span>f(x) is increasing on −∞<x≤0 and decreasing on 0≤x<∞<spanclass=′latex−bold′>(D)</span>f(x) is decreasing on −∞<x≤0 and increasing on 0≤x<∞