Mitochondrial genomes reproduce asexually, which should over time result in an accumulation of harmful mutations and a decline in mitochondrial functionality. However, nuclear genes are hypothesized to coevolve with the rate of mitochondrial decline, eliminating mutational erosion. Such a compensatory measure _____ the organelle’s decline, unlike enzyme-stabilizing accessory proteins, offers an evolutionary explanation of mitochondrial reproduction.
Which choice completes the text so that it conforms to the conventions of Standard English?
Explanation
Context: The main clause "Such a compensatory measure __ the organelle's decline, unlike enzyme-stabilizing accessory proteins, offers an evolutionary explanation" — the blank comes between "measure" and "offers." "Offers" is the main verb; the blank modifies "measure."
Answer: A) counteracting
Why? "Such a compensatory measure counteracting the organelle's decline...offers an evolutionary explanation" — "counteracting" is a participial phrase modifying "measure." The main verb is "offers."
Traps:
- B) counteracted → finite past; creates a comma splice before "offers"
- C) had counteracted → finite past perfect; creates a comma splice
- D) counteracts → finite present; creates a comma splice