题目

△ABC三个顶点所对应的复数分别为z1、z2、z3,复数z满足|z-z1|=|z-z2|=|z-z3|,则z所对应的点是△ABC的( )A.内心B.外心C.重心D.垂心 答案：B(2013·青岛一模)Scientists are still wondering ________ the Egyptians built the pyramids so long ago.A．how it is that B．how is it thatC．it is how that D．that how it is