A:(﹣∞,﹣1)∪(3,+∞)
B:﹣1,3
C:(﹣∞,﹣1∪3,+∞)
D:(﹣1,3)
已知函数fx=ln(21-x+a)(a为常数)是奇函数,则实数a为( )
Daming’s father went to ____ (the great wall).