Before the 1973 oil crisis, the approximate price of a barrel of oil was $3.
That figure describes the broadly stable global price before the October 1973 shock. In March 1974, prices had risen nearly 300%, from about $3 per barrel to almost $12. The crisis followed production cuts and an embargo by Arab oil-exporting countries after the Yom Kippur War.
The change was not a single overnight price move. On October 16, 1973, several oil producers raised the posted price to $3.65 per barrel, after which further cuts and market disruption drove prices sharply higher. The exact price varied by grade, location, contract, and whether a source uses posted or market prices, so the quiz's “approximately” is important.
A common mix-up is confusing the pre-crisis price with the later $3.65 posted price or the roughly $12 price reached in 1974. For a general historical comparison, $3 is the standard answer.