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"): Pentatonix formed in 2011 and subsequently won the third season of NBC's "The Sing-Off," receiving $200,000 and a recording contract with Sony Music.
Relevant evidence: No