In 1 Corinthians 12, what does Paul compare the church to?

Answer: A body

The body is one though it has many parts. 'Now you are the body of Christ, and each of you is a member of it.'

“The body is a unit, though it is composed of many parts. And although its parts are many, they all form one body. So it is with Christ. Now you are the body of Christ, and each of you is a member of it.”— 1 Corinthians 12:12, 12:27 (BSB)