public function store(Request $request, $lecture_id, $subject_id, $topic_id, $knowledgeunit_id)
{
$this->validate($request, ['title' => 'required', 'description' => 'required']);
$knowledgeUnit = KnowledgeUnit::find($knowledgeunit_id);
Log::info('$knowledgeUnit: ' . $knowledgeUnit->title);
$question = new Question();
$question->title = $request->title;
$question->description = $request->description;
$question->knowledge_unit()->associate($knowledgeUnit);
$question->save();
return redirect('/lectures/' . $lecture_id . '/subjects/' . $subject_id . '/topics/' . $topic_id . '/knowledgeunits/' . $knowledgeunit_id . '/questions');
}