下列程序将类C15的对象写入文件file15．txt，选择正确的语句填入下列程序的横线处。 package ch2; import java.util.*; import java.io.*; class C15______ { public iht a; public void setInt(int newa) { a = newa; } } public class Testl5 { pulibc static void main(String[] args) { C15 obj = new C15(); try { FileOutputStream fos =newFileOutputStream("ch2\\filel5.txt"); ObjectOutputStream oos = ObjectOutputStream(fos); Obj.setInt(10); oos.writeObject(obj); oos.close (); fos.close(); } catch(IOException ioe) { ioe.printStackTrace(); } } }

A．implements Runnable

B．implements Sedalizable

C．extends Serializable

D．implements InputStream