Correct Answer: Fortuitous

Solution : The second option is the correct choice.

Catastrophic is commonly used to emphasise the severity and scale of the negative impact, whether it be in the context of natural disasters, accidents, or other unforeseen events. Fortuitous is the correct antonym. It means happening by chance, luck, or fortunate circumstances, which is the opposite of something catastrophic.

The meanings of the other options are as follows:

• Calamity: This is a synonym for catastrophic, referring to a disastrous event or situation.
• Fiasco: This term is similar to catastrophic, indicating a complete failure or disaster.
• Sabotage: This is unrelated to catastrophic and does not serve as an antonym. Sabotage refers to the deliberate destruction or obstruction of something.

Therefore, the correct answer is fortuitous.