Jim tried his best to raise his spirits though he failed the exam.
A:cheer himself up
B:make himself calm
C:keep himself down
刘娜用伏安法测量电阻R的阻值时,并联在电阻R两端的电压表的示数如图甲所示,与电阻R串联的电流表的示数如图乙所示,则电压表的示数为____V;电流表的示数为____ A;电阻R的阻值为____ Ω。
降低大气中的二氧化碳含量,减轻温室效应带来的不利影响,是全人类的共同责任.下列做法无助于降低大气中二氧化碳含量的是( )
你告诉朋友这本书是红色的,可以说