To add values to ion-option from comma separated values

Ionic Framework ionic-v3
1

pic

Here is my StackBliz link https://stackblitz.com/edit/ionic-vdjegs

How to add “Each” values to ion-option from comma separated values

here is my ts file

import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { Validators, FormBuilder, FormGroup,FormControl } from '@angular/forms';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {

  questions:any;

  private form : FormGroup;

  constructor(public navCtrl: NavController,public formBuilder:FormBuilder) {

      this.form = this.formBuilder.group({
     
    });

    this.questions=[
      {id: "1",labels: null,name: "Grade of apple"},
      {id: "2",labels: null,name: "Grade of orange"},
      {id: "3",labels: "grade1,grade2, grade3,grade4",name: "Grade of grape"},
      {id: "4",labels: "yes,no,sometimes",name: "Grade of grape"},
      ]

      this.questions.forEach(que =>{
        let control: FormControl = new FormControl('');
        this.form.addControl(que.id, control);  
      });

  }

  logForm(){
    console.log(this.form.value);
  }

my HTML

>  <ion-item *ngFor="let que of questions; let i=index">
>       <ion-label floating>{{que.name}}</ion-label>
>         <ion-input *ngIf="que.labels == null"  type="text" [formControlName]="que.id"></ion-input>
>           <ion-select *ngIf="que.labels != null" [formControlName]="que.id">
>                  <ion-option >{{que.labels}}</ion-option>
>             </ion-select>
>         </ion-item>
>         <button ion-button  type="submit">Save </button>
>   </form>