1491
these efforts of the crossbow-makers to decrease the friction of the bolt of the crossbow against the stock , as the bolt was driven forward by the bow-string , are traced in all mediaeval crossbows .
 instrument agency: bolt, crossbow
Given options, please tell me the relationships of all the listed entity pairs.Output format is "relation1: word1, word2; relation2: word3, word4". 
Option: component whole, NA, instrument agency, member collection, cause effect, entity destination, content container, message topic, product producer, entity origin 
Text: {0} 
 Entity Pairs:  bolt, crossbow 
Answer:
 instrument agency: bolt, crossbow