d. 
 </PRE>
<h4><a name="Files">Files</a></h4>
<PRE>
 
   None. 
 </PRE>
<h4><a name="Particulars">Particulars</a></h4>
<PRE>
 
   For every line L and point P, there is a unique closest point 
   on L to P.  Call this closest point C.  It is always true that 
   P - C  is perpendicular to L, and the length of P - C is called 
   the &quot;distance&quot; between P and L. 
 </PRE>
<h4><a name="Examples">Examples</a></h4>
<PRE>
 
   1)  Suppose a line passes through the point ( 1, 2, 3 ) and 
       has direc