如何判断一个Socket对象当前是否处于连接状态( ) A: ooleanisConnected=socket.isConnected()&&socket.isBound(); B: ooleanisConnected=socket.isConnected()&&!socket.isClosed(); C: ooleanisConnected=socket.isConnected()&&!socket.isBound(); D: ooleanisConnected=socket.isConnected();