The palace is heavily guarded, because inside its walls ________. A. where sit the European leaders B. the European leaders there sit C. sit the European leaders D. that the European leaders sit 答案:C如图12所示,在一根软铁棒上绕有一个线圈,a、b是线圈的两端,a、b分别与平行导轨M、N相连,有匀强磁场与导轨面垂直,一根导体棒横放在两导轨上,要使a点的电势均比b点的电势高,则导体棒在两根平行的导轨上应该 ( )
A.向左加速滑动
B.向左减速滑动
C.向右加速滑动
D.向右减速滑动