It was his __________ that led him to penury.

Penury means extreme poverty. We need a word describing a habit that would naturally lead someone to become very poor.

Extravagance means spending way more money than needed — like buying ten expensive cars when you only need one! This habit of overspending can easily make someone run out of money and fall into penury.

Let's confirm by checking the other options:

• Flamboyance means being showy or flashy in behaviour/appearance. While being flashy can cost money, it doesn't directly mean overspending.
• Arrogance means being too proud and thinking you're better than others. A bad quality, but it doesn't naturally lead to losing all your money.
• Ebullience means being very cheerful and full of energy. Being happy has nothing to do with becoming poor.

Hence, Option 3: extravagance is correct. If you keep buying things you don't need with all your pocket money and savings, soon you'll have nothing left! That's exactly what this sentence tells us.