Why did the freemasons fall into disrepute in 1826?

The alleged disappearance of ex-mason William Morgan. He threatened the fraternity with divulging certain secrets. It led to a power movement.

Explanation:

The disappearance led to a movement against the fraternity of the Freemasons. His disappearance was blamed on the masons. This contributed to people's paranoia. The body was found and presumptively identified as Morgan's. There is no evidence to suggest that the masons' conspired against a man to take his life. This is why we have a court of law, and evidence should outweigh the "allegations".

d is the best answer for this question.