Why is value not being passed from option?

Question

Vue.js

Component

<template>
           <div class="form-group">
                   <label>Специализация</label>
                <select class="form-control select2bs4" style="width: 100%;" v-model="pr">
                  <option selected="selected" value="1">Стиралки</option>
                  <option value="2">Посудомойки</option>
                  <option value="3">Холодильники</option>
               </select>
              <button type="submit" class="btn btn-block btn-success" @click="submitIt">Начать Сбор</button>
          </div>
</template>

<script>
    export default {
    name: 'reviews-component',
        data(){
            return{
                pr: null
            }
        },
        methods : {
            submitIt: function () {
                console.log(this.pr)
            }
        }
    }
</script>

Why null??
v-model must ensure assignment on change.

Answer 1