一棵二叉树第六层(根结点为第一层)的结点数最多为______个。
参考答案：32
A．They need care and affection.
B．They are fond of round-the-world trips.
C．They are mostly from broken families.
D．They are likely to commit crimes.
（）具有单向导电性。
A、二极管
B、晶体管
C、稳压管
D、电容
