题目

 (08·全国ⅡB篇) The Queen’s English is now sounding less upper-class,a scientific study of the Queen’s Christmas broadcasts has found.Researchers have studied each of her messages to the Commonwealth countries since 1952 to find out the change in her pronunciation from the noble Upper Received to the Standard Received. Jonathan Harrington,a professor at Germany’s University of Munich,wanted to discover whether accent(口音) changes recorded over the past half century would take place within one person.“As far as I know,there just is nobody else for whom there is this sort如图8-7所示，两根光滑金属导轨平行放置，导轨所在平面与水平面间的夹角为θ.整个装置处于沿竖直方向的匀强磁场中．金属杆ab垂直导轨放置，当金属杆ab中通有从a到b的恒定电流I时，金属杆ab刚好静止．则(　　)． 图8-7 A．磁场方向竖直向上 B．磁场方向竖直向下 C．金属杆ab受安培力的方向平行导轨向上 D．金属杆ab受安培力的方向平行导轨向下