由双曲线的标准方程 x25-y29=1可得，a=5，b=3，故虚轴的长为：2 b=6，
故答案为：6．
()DB11/418《电梯日常维护保养规则》标准规定了记录应用钢笔或签字笔填写,不得使用铅笔或圆珠笔。
—Do you watch sports every day?
—No, I don't. _____ I play ping-pong _____ tennis every day. So I can play them well. [ ]
A. But, or
B. And, but
C. But, and
D. And, or
