7286
Using Spurr ' s resin as a mounting medium , we could observe thick specimens with oil immersion objective lens without the use of coverslips , then avoid air bubbles near the specimen .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
 Entities:  
Answer:
 None