title: Connection between pairs and list in scheme
body: <p>I am trying to understand the connection between pairs and lists in scheme. Let's take a look at the following scheme expression:</p>
  
  <pre><code>(((a) (b)) ((c) (d)))
  </code></pre>
  
  <p>I wish to count the number of pairs in the above expression, so I constructed it in the following manner:</p>
  
  <pre><code>(list (list (list 'a) (list 'b)) (list (list 'c) (list 'd)))
   =&gt; (((a) (b)) ((c) (d)))
  
  (list 'a),(list 'b),(list 'c),(list 'd) - 4 pairs
  (list (list 'a) (list 'b)) and (list (list 'c) (list 'd)) - 2 pairs
  (list (list (list 'a) (list 'b)) (list (list 'c) (list 'd))) - 1 pair
  </code></pre>
  
  <p>So far, 7 pairs. Supposed to be 10.
  What am I missing here?</p>