A:π2﹣1
B:π2+1
C:π
D:0
干燥的天气里将毛衣摩擦过的气球靠近头发,会看到如图所示的令人惊奇的现象,这是由于气球摩擦后____,会____不带电的头发.
据图回答:
① ____ A. he B. her C. they D. it
② ____ A. write B. slept C. wash D. fly
③ ____ A. breakfast B. meal C. dinner D. lunch