'Aqualung' is a best-selling album from 1971 by which of the following groups?

'Aqualung' is the fourth studio album by the British rock band Jethro Tull, released on 19 March 1971. It is widely regarded as a concept album featuring a central theme of 'the distinction between religion and God', though the band have said there was no intention to make a concept album, and that only a few songs have a unifying theme. A concept album is an album whose tracks hold a larger purpose or meaning collectively than they do individually.

'Aqualung' is Jethro Tull's best-selling album, selling more than seven million units worldwide. It was generally well-received critically and has been included on several music magazine best-of lists.

Jethro Tull are a British rock band formed in Blackpool, England, in 1967. Initially playing blues rock and jazz fusion, the band soon incorporated elements of hard rock, folk and classical music, forging a signature progressive rock sound. The group’s bandleader, founder, primary composer and only constant member is Ian Anderson (born 10 August 1947), a multi-instrumentalist who mainly plays flute and acoustic guitar, and is also the lead vocalist.