We have been in the school ______ three years ago and Mrs. Lee Has taught us English_______ three years.
A:since; since
B:for; since
C:since; for
D:for; for
读图,如图表示的气候类型中,位于热带的是( )
《公羊传》宣公十五年何休注云:“是故圣人制井田之法而口分之,一夫一妇受田百亩,以养父母妻子,五口为一家……肥墒不得独乐,硗墒(质地差的土地)不得独苦,故三年一换土易居,财均力平,兵车素定,是谓均民力强国家。”材料说明井田制下( )
如图所示电路中滑动变阻器R1的阻值为200Ω,电阻R2阻值为300Ω,电源电压为6V,当滑片由a端滑到b端,电压表的示数的变化范围是( )