阅读下列程序段，不合法的行是______。 class Computer{} class Monitor extends Computer{} class HardDrive extends Computer { pu

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问题阅读下列程序段，不合法的行是______。 class Computer{} class Monitor extends Computer{} class HardDrive extends Computer { public void test() { Monitor a = new Monitor(); Computer b = new Monitor(); HardDrive c = (HardDrive) a; Monitor d = b; } } ①Monitor a = new Monitor(); ②Computer b = new Monitor(); ③HardDrive c = (HardDfive)a; ④Monitor d = b;

选项 A、①②③
B、③④
C、①③④
D、②④

答案B

解析

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本试题收录于：二级Java题库NCRE全国计算机二级分类