32823
The isotope Ac is a transient member of the thorium series decay chain , which begins with the parent isotope Th and ends with the stable lead isotope Pb .
 location: Pb
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Pb 
Answer:
 location: Pb