Angular4 - How to set select option value dynamically

Question

I have a select list with the code -

<select (change)='onGroupChange($event)'>
    <option *ngFor="let group of groups" value={{group.group_name}}>
        {{group.group_name}}
    </option>
</select>

Now I have a group name value saved as a different variable and I want to set that as the select list value if it matches any.

Answer 1

<select (change)='onGroupChange($event)'>
    <option *ngFor="let group of groups" value={{group.group_name}} [selected]="group.group_name==myVariable">
        {{group.group_name}}
    </option>
</select>

Answer 2

<select [(ngModel)]="selectedGroup" (ngModelChange)="onGroupChange($event)">
    <option *ngFor="let group of groups" [value]="group.group_name">
    {{group.group_name}}
    </option>
</select>