8173
Background maintenance is a frequent element of video surveillance systems .
 part of: Background maintenance, video surveillance systems
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:  Background maintenance, video surveillance systems 
Answer:
 part of: Background maintenance, video surveillance systems