rails dynamically generate a form - ruby-on-rails

Question

I'm pretty new to the whole rails MVC concept, and I've been tasked with creating a form which does the following:
takes a test number
shows how many sections there are per test (this is a constant, always 4)
allows a region for the user to enter in their responses for each question in a section. The number of questions in each section changes depending on the test number they get.
I have my view which looks like this:
= form_for [#answer_sheet] do |f|
=f.collection_select(:test_prep_number, Exam.find(:all),:test_prep_number, :test_prep_number, {:include_blank => 'Select your test prep number'})
=f.fields_for :answer_sections do |section_form|
=section_form.label :section
.form-inline
=f.label :A
=radio_button_tag 'answer', 'A'
=f.label :B
=radio_button_tag 'answer', 'B'
=f.label :C
=radio_button_tag 'answer', 'C'
=f.label :D
=radio_button_tag 'answer', 'D'
=f.label :E
=radio_button_tag 'answer', 'E'
My controller looks like this:
def index
#answer_sheet = AnswerSheet.build_with_answer_sections
#answer_section = AnswerSection.new
#section_count = AnswerSection.where("exam_id = ?", params[:test_prep_number).count
end
The issue I'm having right now is I can't seem to wrap my head around creating the correct number of radio buttons. So far, I've managed to generate only one question per section.
I'm assuming I'll need a for loop (which will then require a query to find how many questions per exam section).
Edit: Adding models as requested
Answer sheet model
class AnswerSheet < ActiveRecord::Base
attr_accessible :date, :raw_score, :test_prep_number, :answer_sections, answer_sections_attributes
MAX = 101
validates :test_prep_number, :presence => true
validates :raw_score, :presence => true, :numericality => { :greater_than_or_equal_to => 0, :less_than_or_equal_to => MAX}
validates :date, :timeliness => {:on_or_before => lambda { Date.current }, :type => :date}, :presence => true
belongs_to :user
has_many :answer_sections
Answer Section model
class AnswerSection < ActiveRecord::Base
MAX = 30
attr_accessible :section_score, :answers, :answer_attributes
has_many :answers, :dependent => :destroy
belongs_to :answer_sheet
accepts_nested_attributes_for :answers
validates :section_score, :presence => true, :numericality => { :greater_than_or_equal_to => 0,
:less_than_or_equal_to => MAX }

Answer 1

I would recommend tweaking your models to something the breaks the choice from the users answer:
class Test < ActiveRecord::Base
belongs_to :user
has_many :question
attr_accessible :date, :test_prep_number
validates :test_prep_number, :presence => true
validates :date, :timeliness => {:on_or_before => lambda { Date.current }, :type => :date}, :presence => true
end
class Question < ActiveRecord::Base
MAX = 30
attr_accessible :question_text
has_many :choices, :dependent => :destroy
has_one :answer
belongs_to :test
accepts_nested_attributes_for :answers
end
class Choice < ActiveRecord::Base
attr_accessible :question_id, :choice_text, :correct_choice
belongs_to :question
end
class Answer < ActiveRecord::Base
attr_accessible :choice_id
belongs_to :user
belongs_to :question
end