72÷8=____,再乘4得____.
The teacher's name is Henry Mason. His students call him ________.
“文化大革命”的十年是指( )
如图所示,小磁针静止在通电螺线管的正右方,请根据磁感线方向,在图中标出小磁针的N、S极和电源的正、负极.