In the past twelve months the research m
题型：选择题
问题：
In the past twelve months the research members _____ the effectiveness of many materials in a home building. [ ]
A. had studied
B. would study
C. studied
D. have studied
题型：选择题
图是物理实验中经常用到的滑动变阻器。将它连入电路，移动滑片P，可以改变连入电路中的电阻值，此变阻器是通过改变电阻丝的____________来改变电阻的大小。如果将图示的变阻器连入电路，使滑片向右移动时连入电路的电阻值变小，应将___________两点接入电路中。
