skill-assessment-app/app/views/quiz/_checkbox.html.erb

<%
  question.input_options.each_with_index do | option, i |
  option_id = "#{question.question_id}_#{i}"

  checkbox_html = {class: 'checkbox',
                      id: "answer_#{option_id}",
                    name: "answer[checkbox][]",
                 checked: Array(question.answer).include?(option)
                  }
%>
  <div class="form-group-multiples">
    <%= form.check_box(:answer, checkbox_html, option, '') %>
    <%= form.label(option_id, option) %>
  </div>
<% end %>

<%= render partial: "quiz/answer_errors", locals: {question: question, answer: @answer} %>