Context: Hard rock developed into a major form of popular music in the 1970s, with bands such as Led Zeppelin, The Who, Deep Purple, Aerosmith, AC/DC and Van Halen. During the 1980s, some hard rock bands moved away from their hard rock roots and more towards pop rock, while others began to return to a hard rock sound. Established bands made a comeback in the mid-1980s and it reached a commercial peak in the 1980s, with glam metal bands like Bon Jovi and Def Leppard and the rawer sounds of Guns N' Roses, which followed up with great success in the later part of that decade. Hard rock began losing popularity with the commercial success of grunge and later Britpop in the 1990s.

Question: What are two examples of glam metal bands?
Answer: Bon Jovi and Def Leppard

Question: What two genres cut into hard rock's popularity at the end of the 1980s and early 1990s?
Answer: grunge and later Britpop

Question: What were some hard rock bands of the 1970s?
Answer: Led Zeppelin, The Who, Deep Purple, Aerosmith, AC/DC and Van Halen

Question: What style did some hard rock bands embrace in the 1980s?
Answer: pop rock

Question: When did soft rock become a major form of popular music?
Answer: Unanswerable

Question: Which band became popular in the 1960s?
Answer: Unanswerable

Question: When did some bands move from pop rock to hard rock?
Answer: Unanswerable

Question: What band made a come back in the mid-1990s?
Answer: Unanswerable

Question: When did hard rock replace grunge and Britpop?
Answer: Unanswerable