下面JavaScript代码输出结果正确的是class Animal { constructor(name) { this.name = name; } sayHi() { console.log(`hello ${this.name}`); }}class Dog extends Animal { constructor(name, sound) { this.name = name; this.sound = sound; } bark() { console.log(this.sound); }}let wangcai = new Dog('旺财', '喵喵喵');wangcai.bark();（ ）。