A:,
B:,
C:,
D:,
— _____ Dasan is from Canada, he can speak Chinese very well. — I know he studies Chinese hard.
如图所示,正确使用测电笔的方法是图____,若笔尖接触被测导线时氖管发光,则被测导线是____线。
世界上最早的纸币“交子”出现在北宋时期的( )