A:y=sin2x﹣cos2x
B:y=sin2x+cos2x
C:y=sin2x﹣2cosx
D:y=sin2x+2cosx
The students carried their books away from the school ____ ____ .
图为人体消化、呼吸、循环、泌尿等系统的生理活动示意图,请据图回答: