In triangle XYZ, XW is drawn as a perpendicular line from X to the opposite side.<br><br>
&bull; From the figure: XW is the perpendicular height from vertex X to side YZ.<br>
&bull; XW meets YZ at point W, forming a right angle.<br>
&bull; Therefore, if the height is XW, the base is YZ.<br><br>
Final Answer: C: YZ