—Amanda, you look tired today. What's wrong?—I worked______ late ______ I didn't go to bed until midnight yesterday.
A:too; to
B:so; that
C:not only; but also
D:such; that
用已调好的托盘天平测量物体的质量时,应将砝码放在天平的 ____盘.当放入20g、10g和5g的砝码各一个,游码拨到如图所示的位置时,指针恰好指在分度盘的中线处,则被测物体的质量为 ____ g.
光的世界是丰富多彩的,以下关于光现象的说法正确的是(