Question: Pentatonix, the five-member American a cappella group lost their vocalist Avi Kaplan in 2017 at the same time as their tribute to which group received over 250 million views?
Sentence (from "Pentatonix World Tour 2016"): Pentatonix World Tour 2016 (titled as Pentatonix World Tour 2017 for the shows in 2017) was the second headlining concert tour by American a cappella group Pentatonix to promote their eponymous album.
Relevant evidence: No