17301
The reaction is followed spectrophotometrically by measuring the change in absorbance ( Delta A ) at 420 nm using a fixed time method ( 70 s ) .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None