Final answer:
The Beatles' album 'Rubber Soul' was the inspiration behind the Beach Boys' 'Pet Sounds'. Brian Wilson sought to match its artistic depth, leading to the creation of one of the most influential albums in music history.
Step-by-step explanation:
The album by The Beatles that inspired the Beach Boys' concept album "Pet Sounds" is b) Rubber Soul. Brian Wilson of the Beach Boys was particularly moved by the sophisticated musical depth and lyrical content of Rubber Soul, which prompted him to create an album that could stand up to its artistic level. The result was "Pet Sounds", now regarded as one of the most influential albums in the history of popular music. Although "Sgt. Pepper's Lonely Hearts Club Band" is another hallmark album, it was actually released after "Pet Sounds", and was influenced by the Beach Boys' work in return.