A:①②
B:②③
C:②④
D:③④
63÷(34-25)=____
——More and more students wear glasses in our school these days.——I agree with you. Students ___ keep on doing eye exercises to protect their eyes.
端午节赛龙舟是我国民间传统习俗.运动员用浆向后划水,水给浆一个向前的力,使龙舟向前行驶的力的施力物体是( )
点P在平面直角坐标系的位置如图所示,将点P向下平移a个单位得点P′,若点P′到x轴和y轴的距离均相等,且点P′在第三象限,则a的值是____