[Rails] Locals does not pass in var in partial

Hi everyone,

Here is code in form.html.erb for partial view (controller rfqs).
Local var :sid was defined as the id of the record and it should be
passed into the partial view standards.html.erb as a local var.

<% @rfq.standards.each do |r| %>
<p><%= render :partial => 'standards', :locals => { :f =>
f, :sid => r.id } %></p>
<% end %>

Here is the standards partial view:

<%= f.association :standards, :collection =>
Standard.active_std.all(:order => 'name'), :label_method
=> :name, :value_method => :id, :prompt => "Choose std", :label =>
"standard：", :include_blank => true, :selected => sid %>

When standards rendered, there is an error saying that sid was not
defined. I did extensive search online about how to use :locals and
could not figure out what causes error. Any thoughts about the error?
Thanks.