1. class SuperFoo { 2. SuperFoo doStuff(int x) { 3. return new SuperFoo(); 4. } 5. } 6. 7. class Foo extends SuperFoo { 8. //insert code here 9. } 下面哪三项分别插入到第8行,可以编译?()
A. int doStuff() { return 42; }
B. int doStuff(int x) { return 42; }
C. Foo doStuff(int x) { return new Foo(); }
D. SuperFoo doStuff(int x) { return new Foo(); }