运行如下代码，点击按钮Greet后label框内显示“Hello, World!”字样。（ ）

import tkinter as tk

def greet():

    label.config(text="Hello, World!")

root = tk.Tk()

label = tk.Label(root, text="")

button = tk.Button(root, text="Greet", command=greet)

label.pack()

button.pack()

root.mainloop()