一道挺有意思的题

package main

import (
    "encoding/json"
    "fmt"
)

type AutoGenerated struct {
    Age   int    `json:"age"`
    Name  string `json:"name"`
    Child []int  `json:"child"`
}

func main() {
    jsonStr1 := `{"age": 14,"name": "potter", "child":[1,2,3]}`
    a := AutoGenerated{}
    json.Unmarshal([]byte(jsonStr1), &a)
    aa := a.Child
    fmt.Println(aa)
    jsonStr2 := `{"age": 12,"name": "potter", "child":[3,4,5,7,8,9]}`
    json.Unmarshal([]byte(jsonStr2), &a)
    fmt.Println(aa)
}

选项：
A：[1 2 3] [1 2 3]
B：[1 2 3] [3 4 5]
C：[1 2 3] [3 4 5 6 7 8 9]
D：[1 2 3] [3 4 5 0 0 0]

应该选哪个呢？为什么？