复数a+bi(a,b∈R)等于它共轭复数的倒数的充要条件是( )
据报道,5月28日参观2010上海世博会的人数达35.6万﹒用科学记数法表示数35.6万是( )
The work is difficult so I think it's____(possible)to finish it in an hour.