This is a real head-scratcher... The correct answer is ..... ( | IELTS ZONE 9.0

This is a real head-scratcher... The correct answer is ..... (drum roll)...
A!
That's right... even though the text mentions 'interpretation'. There is only one (not many, surely not conflicting). If something cracks, it means it doesn't hold true.... So, the cracks have been spreading ever since means there have been increasing (=mounting) deficiencies (=weaknesses). One example is that other scientists could NOT replicate (=get the same) results as claimed. Give yourself a pat on the back if you got this one right...