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We focus on one speed-up element in the design of unification algorithms : avoidance of copying of unmodified subgraphs .
 part of: speed-up element, unification algorithms
Given options, please tell me the relationships of all the listed entity pairs.Output format is "relation1: word1, word2; relation2: word3, word4". 
Option: conjunction, feature of, hyponym of, used for, part of, compare, evaluate for 
Text: {0} 
 Entity Pairs:  speed-up element, unification algorithms 
Answer:
 part of: speed-up element, unification algorithms