title: Comparing sizes of sets that are keys and values of a map
body: <blockquote>
    <p>Consider a map  m, where  m  is of type  HashMap  or  TreeMap.  Suppose  s1  and  s2  are both sets, of type  HashSet  or  TreeSet, where  s1  is the set of keys in  m, and  s2 is the set of corresponding values in  m.  Which  must  be true?</p>
  </blockquote>
  
  <p>a. s1.size() > s2.size()</p>
  
  <p>b. s1.size() &lt;= s2.size()</p>
  
  <p>c. s1.size() >= s2.size()This is the correct answer.</p>
  
  <p>d. s1.size() == s2.size()</p>
  
  <p>e. s1.size() &lt; s2.size()</p>
  
  <p>I had thought it would be "b" since a key can have many values, but it turns out the answer is c, where there may be more keys than values. However, I'm having problems understanding the answer provided (c)—could anyone help me understand why b is wrong and c is right?</p>