A:齐桓公
B:汉景帝
C:隋文帝
D:唐太宗
海外华人常自豪地称自己为“炎黄子孙”是因为( )
在“测定金属丝电阻率”的实验中,需要测出其长度L、直径d和电阻R.
—Which is more useful, reading or writing?
—I think _______ of them are useful.