Placeholder for Select dropdown not working

I have searched and try many of the solutions that have been given in this forums but I still can’t seem to get my code to display the placeholder.
enter image description here

I have use "" in the value, as well as disable and hidden, also as well as not creating a variable and just typing the phrase. Maybe I just need a new set of eyes to help me see what I may be missing.

here’s the output
enter image description here

I have try some of the top results when doing a search and they don’t seem to work

*****update

so 3 out of the five work, the only thing I can think of is the array I’m using *ngFor… I think I read something about that… for the other two is the same code as above and fixed to the first answer but for some reason they placeholder wont work.

>Solution :

You can create an option with value set as undefined and disabled, so on first load, it will appear as a label, after that the user can select the correct value!

<form #f="ngForm" (ngSubmit)="save()">
  <select
    [(ngModel)]="selected"
    name="valueCheck"
    (change)="valueChange($event)"
  >
    <option [ngValue]="undefined" disabled>Choose...</option>
    <option
      *ngFor="let obj of stud"
      [ngValue]="obj.rnNo"
      [selected]="obj.rnNo == selected"
    >
      {{ obj.name }}
    </option>
  </select>
  <button type="submit">submit</button>
  <button (click)="clear()">clearValue</button>
</form>
<h3>{{ selected }}</h3>

ts

...
export class AppComponent {
    selected!: number;
...

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