Today is _____ day at school.[ ]
A. first
B. the my first
C. my first
D. my the first
答案:C
电炉工作时,两端电压是220V,通过电阻丝的电流是2A,则1min电流做功______J.
小张和小王住在同一幢楼里,这幢楼相邻两层间的楼梯级数相同.小张住4楼,回家要走54级楼梯,小王住在8楼,小王回家要走______级楼梯.