根据下列程序的执行结果，可以断定划线部分的修饰符应为______。执行结果： i9a football is created. a football is created. i=10 a football is destroyed. a football is created. i=20 a football is destroyed. a football is destroyed. 源程序： #include＜iostream.h＞ class Football
public: Football( )cout＜＜"a football is created."＜＜endl; ～Football( )tout＜＜"a football is destroyed."＜＜endl; ; void func(int i)
______Football f1; Football f2; cout＜＜"i="＜＜i＜＜endl;