每年的6、7、8三个月是北半球的（　　）

A．春季

B．夏季

C．秋季

D．冬季

选择正确的语句填在下列程序的横线处，使程序正常运行。package ch1;import java. io. *;import j ava. util. *;class C45 implements Seritizable ______Public Thread t = new Thread(new T45(), "t"); public intcnt = 0; public C45() { t. start ( )class T45 implements Runnable public int[] a = new int[4]; public void run() { for(int i - 0; i ＜ 4; i++) { a[i] - i +4; } }}public class ex45{ static String fileName = "ch1\\file45.txt"; public static void main(String[] args) throws Exception { C45 obj = new C45 (); FileOutputStream fos = new FileOutputStream(fileName); ObjectOutputStream oos = new ObjectOutputStream(fos); oos. writeObject (obj); oos.clese (); fos.close (); System. out, println (obj . toString ( ) ); } }

A．transient

B．protected

C．package

D．final