2. 为了让 Dog 类的构造函数能正确地调用其父类 Animal 的构造方法，横线线处应填入（ ）。
class Animal {
public:
std::string name;
Animal(std::string str) : name(str) {
std::cout << "Animal created\n";
}
virtual void speak() {
cout << "Animal speaks" << endl;
}
};
class Dog : public Animal {
std::string breed;
public:
Dog(std::string name, std::string b) : _________________, breed(b) {
std::cout << "Dog created\n";
}
void speak() override {
cout << "Dog barks" << endl;
}
};
int main() {
Animal* p = new Dog("Rex", "Labrador");
p->speak();
delete p;
return 0;
}