下列函数中,y一定是关于x的二次函数的是( )
A:y=ax2+bx+c
B:y=2x2
C:y=2x2
D:y=x2+1x+1
She could speak ________ Japanese ________ Chinese, so I had to talk with her in English.
随着对环境保护的重视,对农业害虫可采取综合防治的措施。为除去有害于农作物的某种害虫I而引入捕食蜘蛛后,对这两个种群数量变化进行调查,得出如图所示的结果。下列关于对此过程的推理中正确的是( )