一把刻度准确的杆秤的秤砣磨损了一些,则称出的结果________。(偏大、偏小或不变)
偏大
A.减小投影仪与屏幕间的距离,下调凸透镜,减小凸透镜到物体间的距离
B.减小投影仪与屏幕间的距离,上调凸透镜,增大凸透镜到物体间的距离
C.增大投影仪与屏幕间的距离,下调凸透镜,减小凸透镜到物体间的距离
D.增大投影仪与屏幕间的距离,上调凸透镜,增大凸透镜到物体间的距离
They were walking ________ a forest after they swam _______ the river .
A.through, cross
B.across ,through
C.through, across
D.across, across