刃磨米制蜗杆精车刀时，刀头宽度可用公式形=0.697m，(当h=2r2mx时)计算。( )
参考答案：对
我国某地有一口井，一年中只有一天太阳可直射井底，该地位于[ ]
A．赤道上
B．北回归线上
C．南回归线上
D．北极圈上
Parents care about children’s education more than anything else.
A. their B. them C. theirs
