单项选择题

A.classAnimal{AnimalgetOne(){returnnewAnimal();}}2.classDogextendsAnimal{3.//insertcodehere4.}5.6.classAnimalTest{7.publicstaticvoidmain(String[]args){8.Animal[]animal={newAnimal(),newDog()};9.for(Animala:animal){10.Animalx=a.getOne();11.}12.}13.}和代码:3a.DoggetOne(){returnnewDog();}3b.AnimalgetOne(){returnnewDog();}第3行中插入的哪项将编译且运行无异常?()
A.3a行
B.3b行
C.3a行或3b行
D.既非3a,也非3b