已知3个类O、P和Q，类O中定义了一个保护方法F1和公有方法F2；类P中定义了一个公有方法F3，类P为类O的派生类；类O为类P的派生类，它们的继承方式如下，在关于类P的描述中正确的是(43)；在关于类Q的描述中正确的是(44)。

 class P：private O(…)

 class Q：protected P(…)

(53)

(73)

(72)

(71)

(70)

(68)

In low-speed network，it is usually adequate to wait for congestion to occur and then react to it bytelling the source of packets to slow down．In high-speed networks，this approach often works poorly，because in the(71) between sending the notification and notification arriving at the source，thousands of additional(72) may arrive．In ATM network，a major tool for preventing(73)is(74)control．When a host wants a new virtual(75)，it must describe the traffic to be offeredand the service expected．

(69)

(67)

电视信号的标准也称电视的制式，制式的区别在于其帧频的不同、分辨率的不同、信号带宽及载频的不同、彩色空间的转换关系不同等。我国电视采用的制式是(58)，对应帧频是(59)帧/妙，对应分辨率为(60)。

(66)

(65)

(64)