Select the most appropriate option to fill in the blank.

Being a millionaire, he is leading a ______ life.

luxurious

The correct option to fill in the blank is luxurious.

The word "luxurious" means characterized by great comfort and opulence. It is the most appropriate word to use in this context, as it conveys the meaning of the millionaire living a very comfortable and extravagant lifestyle.

The other options are not as appropriate.

• Destitute means lacking the basic necessities of life. This is not the right word to use, as it does not make sense to say that a millionaire is destitute.
• Expensive means costing a lot of money. This is not the right word to use, as it does not convey the same meaning as "luxurious."
• Conducive means helpful or appropriate to a particular activity. This is not the right word to use, as it does not make sense to say that a millionaire's life is conducive to luxury.