Task: Text Categorization
Input (English): Question: The color centers or F centers are produced: 
 Options:  <0> Exclusively in crystals that contain fluorine. <1> By heating a crystal in the vapor of an alkali metal. <2> By cooling a crystal in the vapor of an alkali metal. <3> By heating a crystal in the presence of fluorine. <4> By cooling a crystal in the presence of fluorine.
Output (English): chemistry