—It's so late. Why not write the report tomorrow?—But I don't know _______ I can do it if not now.
A:why
B:when
C:how
D:where
如图,在Rt△ABC中,∠A=90°,∠ABC=2∠C,BD=CD.求证:CD=2AD.
要测量某电阻的阻值,实验桌上有下列器材:电流表A(0﹣0.6A),电压表V(0﹣3V),电源4.5V,滑动变阻器R,开关,导线,待测电阻Rx(约6Ω左右).实验要求:多测几组数据且两电表都不能超过其量程.