定义在R上的奇函数fx满足:当x>0时,fx=2013x+log2013x,则方程fx=0的实数根的个数是( )
It is nearly 50 years ______ the People's Republic of China was founded.
对于全集U的子集M,N,若M是N的真子集,则下列集合中必为空集的是( )