Which of the following is NOT a cause that led to the disaster at Bhopal in 1984a.technical incompetence of plant engineerb.improper setting of alarm clockc.pouring of water into the MIC tankd.non-functioning of refrigeration unit and flare tower

The option that is NOT a cause that led to the disaster at Bhopal in 1984 is "b. improper setting of alarm clock".

Here's why:

a. Technical incompetence of plant engineer: This was indeed a cause. The plant was not properly maintained and the staff was not adequately trained, leading to a lack of understanding of the potential dangers and how to prevent them.

c. Pouring of water into the MIC tank: This was a direct cause of the disaster. Water entered the tank containing the highly reactive chemical Methyl Isocyanate (MIC), causing a chemical reaction that led to the release of a large volume of toxic gas.

d. Non-functioning of refrigeration unit and flare tower: The refrigeration unit, which was designed to cool the MIC and slow down any reactions, was not functioning properly. The flare tower, which was supposed to burn off any escaping gas, was also out of order. Both of these failures contributed to the disaster.

b. Improper setting of alarm clock: This is not a cause. The disaster was not caused by someone oversleeping or failing to respond to an alarm clock. It was caused by serious technical and operational failures.