A:①②
B:②③
C:②④
D:③④
若x=1满足不等式ax2+2x+1<0,则实数a的取值范围是( )
电能表接在电路中是为了测量( )
—____ do you celebrate the Mid-Autumn Festival?
—We enjoy the full moon and eat moon cakes.
碘是一种由碘分子构成的非金属,某同学利用碘进行了如图所示的实验:①把少量的固体碘放在湿润的馒头上,发现馒头会变蓝色;②再取少量的碘溶解在水中,用馒头去蘸取碘液,发现馒头也会变蓝色。则: