Scientists have recently discovered that certain bacteria can not only survive in extremely acidic environments, but also are thriving there, metabolizing compounds that are toxic to most other life forms.

The correct answer to the question "Scientists have recently discovered that certain bacteria can not only survive in extremely acidic environments, but also are thriving there, metabolizing compounds that are toxic to most other life forms." is Option B: but also thrive there, metabolizing compounds that are toxic to most other life forms..

The other options — A) but also are thriving there, metabolizing compounds that are toxic to most other life forms., C) and also thriving there, and metabolizing compounds that are toxic to most other life forms., D) and also thrive there, to metabolize compounds that are toxic to most other life forms. — are incorrect for this GMAT Exam Prep question. As explained above: The original sentence violates parallelism with 'not only... but also'. The structure requires 'can survive' to be parallel with 'can thrive'. Option B correctly uses 'thrive' to maintain parallel st…