如何使用多重继承实现多态行为？

class Animal:
    def speak(self):
        pass

class Dog(Animal):
    def speak(self):
        return "Woof!"

class Cat(Animal):
    def speak(self):
        return "Meow!"

class Duck(Animal):
    def speak(self):
        return "Quack!"

class Car:
    def drive(self):
        pass

class ElectricCar(Car):
    def drive(self):
        return "Electric car is driving."

class GasCar(Car):
    def drive(self):
        return "Gas car is driving."

class Vehicle:
    def __init__(self, animal, car):
        self.animal = animal
        self.car = car

    def make_sound(self):
        return self.animal.speak()

    def move(self):
        return self.car.drive()

# Create a Vehicle object with a Dog and an ElectricCar
dog_car = Vehicle(Dog(), ElectricCar())
print(dog_car.make_sound())  # Output: Woof!
print(dog_car.move())  # Output: Electric car is driving.

# Create a Vehicle object with a Cat and a GasCar
cat_car = Vehicle(Cat(), GasCar())
print(cat_car.make_sound())  # Output: Meow!
print(cat_car.move())  # Output: Gas car is driving.