问题
选择题
I have been living in the United States for twenty years, but seldom ___ so lonely as now. [ ]
A. have I felt
B. I had felt
C. I have felt
D. had I felt
答案
答案：A
搜题请搜索小程序“爱下问搜题”
I have been living in the United States for twenty years, but seldom ___ so lonely as now. [ ]
A. have I felt
B. I had felt
C. I have felt
D. had I felt
答案：A
在“描绘小电珠的伏安特性曲线”实验中，所用器材有：小电珠（2.5V，0.6W），滑动变阻器，电流表，学生电源，开关，导线若干．
①利用小电珠的标称值可估算出小电珠正常工作时的电阻值约为______Ω．（计算结果保留2位有效数字）
②请根据实验原理图甲完成实物图乙中的连线．
③开关闭合前，应将滑动变阻器的滑片P置于______端．为使小电珠亮度增加，P应由中点向______端滑动．
④下表为电压等间隔变化测得的数据，为了获得更准确的实验图象，必须在相邻数据点______间多测几组数据（请填写“ab”“bc”“cd”“de”或“ef”）．
| 数据点 | a | b | c | d | e | f |
| U/V | 0.00 | 0.50 | 1.00 | 1.50 | 2.00 | 2.50 |
| I/A | 0.000 | 0.122 | 0.156 | 0.185 | 0.216 | 0.244 |
