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They differentiate themselves by only offsetting using Certified Emission Reduction s ( CERs ) which have been issued every time the United Nations prevents one tonne of Carbon dioxide equivalent being emitted through carbon projects registered with the Clean Development Mechanism ( CDM ) Research Clear has a research arm which has produced a variety of reports on subjects such as the carbon footprint of the UK 's speed hump population , and the carbon footprint of a Segway PT and a Formula One car .
 organization: United Nations
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: United Nations 
Answer:
 organization: United Nations