挑战习题
1/5单选题
难度:

1.如图所示,当开关S闭合时电磁铁和物体ab相互吸引,则正确的说法是 (    )
A ab一定是磁铁,且a端一定是N极。
B ab一定是磁铁,且a端一定是S极
C ab可能是磁铁,且a端是S极
D ab仅是一块铁,而不是磁铁
提示1:
IOagueaNrueUtea6kOeahOato+i0n+aege+8jOWPr+S7peWIpOaWreWHuuWGsuWQkeaIkeS7rOi/meS4quaWueWQkeeahOeUtea1geaYr+WQkeS4i+eahA==
提示2:
IOagueaNruWuieWfueWumuWIme+8jOiuqeWPs+aJi+W8r+absueahOWbm+aMh+WSjOeOr+W9oueUtea1geeahOaWueWQkeS4gOiHtO+8jOmCo+S5iOS8uOebtOeahOWkp+aLh+aMh+aJgOaMh+eahOaWueWQkeWwseaYr+eOr+W9oueUtea1geS4reW/g+i9tOe6v+S4iuejgeaEn+e6v+eahOaWueWQke+8jOWPiuieuue6v+euoeWPs+S+p+WwseaYr07mnoE=
提示3:
IOWmguaenGFi5piv5Liq56OB6ZOB77yM5Lik6ICF55u45LqS5ZC45byV77yM5qC55o2u5byC5ZCN56OB5p6B55u45LqS5ZC45byV77yM5omA5LulYeerr+aYr1PmnoHjgILlpoLmnpxhYuaYr+S4gOWdl+mTge+8jOmAmueUteieuue6v+euoeW4puacieejgeaAp++8jOS5n+WPr+S7peebuOS6kuWQuOW8leOAgg==
正确答案:Qw==
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