Concept:The word "prudent" means wise and careful, especially with money, so its opposite must mean spending wastefully.
Explanation:In the given sentence, the underlined word is "prudent".
A prudent person manages resources sensibly and avoids unnecessary risks.
The word that is most nearly opposite in meaning is "extravagant".
"Extravagant" describes someone who spends too much money or uses resources carelessly.
This fits perfectly in the gap because it contrasts directly with prudent behaviour.
The other options are not suitable.
"Mean" means selfish or unwilling to share, not the opposite of prudent.
"Thoughtful" and "mindless" do not relate to careful or wasteful spending.
Therefore, the correct choice is "extravagant".
Answer:B. extravagant