Step 1: Understanding the Question:
The question asks which Arab nation counted as the richest, which in this context means the highest income per person, not simply the largest overall economy.
Step 2: Key Facts:
Richness of a nation is usually judged by income per person rather than total GDP, since a country can have a huge total economy but a low population-adjusted income, or a small population with a very high per person income. Several Gulf Arab states earn most of their income from oil and gas exports and have small populations relative to their resource wealth.
Step 3: Detailed Explanation:
Qatar sits on some of the largest natural gas reserves in the world, and its exports of liquefied natural gas, combined with a very small citizen population, pushed its income per person to among the very highest in the world by the mid 2000s, ahead of its Gulf neighbours. Saudi Arabia has by far the largest total economy in the Arab world thanks to its oil reserves, but it also has a much larger population to share that income across, so its per person income trails Qatar's. The United Arab Emirates and Kuwait are also oil rich Gulf states with high living standards, but neither matched Qatar's income per person once its gas revenues began flowing at scale.
Step 4: Final Answer:
Qatar was the richest Arab nation by income per person, so the answer is option (3).