Classify the relation of question with context to one of these categories: 1) award received, 2) based on, collection, 3) conflict, 4) constellation, 5) convicted of, 6) date of death, 7) director, 8) drafted by, 9) educated at, 10) medical condition, 11) military branch, 12) narrative location, 13) occupation, 14) original network, 15) parent company, 16) point in time, 17) production company, 18) residence, 19) series, 20) service entry, 21) sex or gender, 22) spouse, 23) standards body question.

Context : The BMP-3 is designed and produced by the Kurganmashzavod (``Kurgan Machine Building Plant'') some variants however are built by the Rubtsovsk Machine Building Plant (RMZ), for example the BRM-3K. 
Question : What year was BMP-3 introduced?
service entry

Context : The first astronomer to record the Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. 
Question : What constellation is where Butterfly Cluster is?
constellation

Context : ``Obsidian Butterfly'' (a folkloric reference to bats) is one of the English translations of Itzpapalotl, rendering the nightclub and the book eponymous. 
Question : What series is the episode Obsidian Butterfly part of?

series