show select option as default

I laravel I want to create a select box which wants has 'select option,Approved,Rejected' But I always shows Approved as default option in form

echo Form::select('request_status',[''=>'Select option','4'=>'Approved','7'=>'Rejected'],null,['class'=>'request_status report_filter default']);

How to make select option as default in laravel 5.3

via Chebli Mohamed