在堆栈类Sharedstack的定义中，为了保证堆栈在并发操作中数据的正确性，应在下画线处填入的修饰符是(两个下画线的填写内容相同)______。
public class SharedStack
______int idx=0;
______char[]data=new char[10];
public synchtonized void push(char c)......
public synchronized void pop()......)

A．class Test implements Runnable
public void run()
public void someMethod[]B．class Test implements Runnable(
public void run();C．class Test implements Runnable(
public void someMethod[];D．class Test implements Runnable
public void someMethod()

A．repaint
B．println
C．paint
D．show