当通电导体与磁力线间的夹角为()时,导体受到的电磁力最大。
A.30°
B.0°
C.60°
D.90°
参考答案:D
胎儿血液中出现高浓度的下列哪种免疫球蛋白表明有宫内感染 ()
A.IgG
B.IgA
C.IgM
D.IgE
E.IgD
Things are ________ on Mars ________ on Earth because of the different gravity.
A.much lighter; than that
B.much lighter; than those
C.not so light; as that
D.not so light; as those