如何显示多个foreach？

I have changed the model Exams to save ExamQuestions from hasMany to belongsTo and here is how I've modified my controller. I'm getting a Invalid argument supplied for foreach() in the View.

Here is the Exam model that I've changed

     public function questions()
  {
      return $this->belongsTo(ExamQuestion::class, 'exam_questions');
  }

Here is my controller

public function exam($course_id, Request $request)
        {
            $course = Course::where('id', $course_id)->firstOrFail();
            $answers = [];
            $exam_score = 0;
            foreach ($request->get('questions') as $question_id => $answer_id) {
                $question = ExamQuestion::find($question_id);
                $correct_answer = ExamOption::where('exam_question_id', $question_id)
                    ->where('id', $answer_id)
                    ->where('is_correct', 1)->count() > 0;
                $answers[] = [

                    'exam_question_id' => $question_id,
                    'exam_option_id' => $answer_id,
                    'corect' => $correct_answer
                ];
                if ($correct_answer) {
                    $exam_score += $question->score;
                }
            }

            $exam_result = ExamResult::create([
              'exam_id' => $course->exam->id,
              'employee_id' => \Auth::id(),
              'result' => $exam_score,
            ]);
            $exam_result->answers()->createMany($answers);

            $get_reslts_score= Exam::with('exam_results')->first();
            $x = $get_reslts_score->passing_grade;

            if($exam_result->result >= $x) {
              $exam_result->is_complete = 1;
              $exam_result->save();
}

            return redirect()->route('learn.show', [$course, $request])->with('message', 'Test score: ' . $exam_score);
        }

Here is my view

  <h3>@if ($courses->exam)</h3>
  <hr/>
    <div class="row">
      <div class="col-xs-12 form-group">

      <form action="{{ route('exam.save', [$courses->id]) }}" method="post">
      {{ csrf_field() }}


        @foreach($courses->exam->questions as $question)

        <br>{{$loop->iteration}} . {{$question->question}}</b>
        </br>

        @foreach($questions->exam_options as $option)
        &nbsp;<input type="radio" name="question[{{ $question->id }}]" value="{{ $option->id }}"/>&nbsp;&nbsp;{{ $option->text }}</br>
        @endforeach


        <br>
        @endforeach

  <h3>@if ($courses->exam)</h3>
  <hr/>
  <div class="row">
      <div class="col-xs-12 form-group">
         <form action="{{ route('exam.save', [$courses->id]) }}" method="post">
              {{ csrf_field() }}
           @foreach($courses->exam->questions as $questions)
               <br>{{$loop->iteration}} . {{$questions->question}}</b>
               </br>

            @foreach($questions->exam_options as $option)
               &nbsp;<input type="radio" name="question[{{ $questions->id }}]" value="{{ $option->id }}"/>&nbsp;&nbsp;{{ $option->text }}</br>
            @endforeach
            <br>
          @endforeach

If it did not work please check your model relationships returning value or not. Using parent to recursively go through the full array you can go up to any level of depth here